According to the Maudsley Guidelines, it is recommended to administer a test dose for all first generation antipsychotics. Following the test dose, it is advised to wait 4-10 days before administering the next dose.

, coma, respiratory depression (rare)

Biogenic Amines: Understanding the Neurotransmitters

Biogenic amines are a class of compounds that are derived from amino acids. These compounds play a crucial role in the functioning of the nervous system. Biogenic amine neurotransmitters include catecholamines (adrenaline, noradrenaline, and dopamine), serotonin, and histamine. A useful mnemonic to remember these neurotransmitters is HANDS (Histamine, Adrenaline, Noradrenaline, Dopamine, Serotonin).

Catecholamines are involved in the body’s response to stress and are responsible for the fight or flight response. Adrenaline and noradrenaline are catecholamines that are released by the adrenal glands in response to stress. Dopamine is involved in the reward system of the brain and is associated with pleasure and motivation.

Serotonin is a neurotransmitter that is involved in mood regulation, appetite, and sleep. It is also involved in the regulation of pain and the perception of pain.

Histamine is involved in the immune response and is responsible for the symptoms of allergies. It is also involved in the regulation of sleep and wakefulness.

Understanding the role of biogenic amines in the nervous system is crucial for the development of treatments for neurological and psychiatric disorders.

Antipsychotic drugs are known to cause weight gain, but some more than others. The reason for this is not due to a direct metabolic effect, but rather an increase in appetite and a decrease in activity levels. The risk of weight gain appears to be linked to clinical response. There are several suggested mechanisms for this, including antagonism of certain receptors and hormones that stimulate appetite. The risk of weight gain varies among different antipsychotics, with clozapine and olanzapine having the highest risk. Management strategies for antipsychotic-induced weight gain include calorie restriction, low glycemic index diet, exercise, and switching to an alternative antipsychotic. Aripiprazole, ziprasidone, and lurasidone are recommended as alternative options. Other options include aripiprazole augmentation, metformin, orlistat, liraglutide, and topiramate.

Hyponatremia in Psychiatric Patients

Hyponatremia, of low serum sodium, can occur in psychiatric patients due to the disorder itself, its treatment, of other medical conditions. Symptoms include nausea, confusion, seizures, and muscular cramps. Drug-induced hyponatremia is known as the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH), which results from excessive secretion of ADH and fluid overload. Diagnosis is based on clinically euvolaemic state with low serum sodium and osmolality, raised urine sodium and osmolality. SSRIs, SNRIs, and tricyclics are the most common drugs that can cause SIADH. Risk factors for SIADH include starting a new drug, and treatment usually involves fluid restriction and sometimes demeclocycline.

Alternative Routes of Administration for Antidepressants

While most antidepressants are taken orally, there are a few alternative routes of administration available. However, it is important to note that these non-oral preparations should only be used when absolutely necessary, as they may not have a UK licence.

One effective alternative route is sublingual administration of fluoxetine liquid. Buccal administration of selegiline is also available. Crushed amitriptyline has been shown to be effective when administered via this route.

Intravenous administration is another option, with several antidepressants available in IV preparations, including citalopram, escitalopram, mirtazapine, amitriptyline, clomipramine, and allopregnanolone (which is licensed in the US for postpartum depression). Ketamine has also been shown to be effective when administered intravenously.

Intramuscular administration of flupentixol has been shown to have a mood elevating effect, but amitriptyline was discontinued as an IM preparation due to the high volumes required.

Transdermal administration of selegiline is available, and suppositories containing amitriptyline, clomipramine, imipramine, and trazodone have been manufactured by pharmacies, although there is no clear data on their effectiveness. Sertraline tablets and doxepin capsules have also been given rectally.

Amantadine and QTc Prolongation

Amantadine is a medication used to treat Parkinson’s disease and influenza. It has been associated with QTc prolongation, which can increase the risk of Torsades de points. Therefore, caution should be exercised when prescribing amantadine to patients with risk factors for QT prolongation. If a patient is already taking amantadine and develops a prolonged QTc interval, the medication should be discontinued and an alternative treatment considered. It is important to monitor the QTc interval in patients taking amantadine, especially those with risk factors for QT prolongation.

Alcohol withdrawal is a common issue in the UK, and Chlordiazepoxide (Librium) is a benzodiazepine that is frequently used to treat it. This medication is safe, effective, and allows for flexible dosing. Acamprosate is another medication that is licensed for the treatment of alcohol cravings, while Carbamazepine may be used in cases where there is a risk of withdrawal seizures. Chlormethiazole, also known as Heminevrin, was once widely used for alcohol withdrawal but is now less commonly used due to its relative toxicity. Chlorpromazine, a typical antipsychotic, is not typically used in uncomplicated cases of alcohol withdrawal.

Agonists and Antagonists in Pharmacology

In pharmacology, an agonist is a substance that binds to a receptor and triggers a biological response. On the other hand, an antagonist is a substance that blocks the effects of an agonist. A partial agonist produces a response but cannot produce the maximum response even at high doses.

Competitive antagonists bind to the receptor in a reversible way without affecting the biological response. They make the agonist appear less potent. Inverse agonists, on the other hand, have opposite effects from those of full agonists. They are not the same as antagonists, which block the effect of both agonists and inverse agonists.

Full agonists display full efficacy at a receptor. Some substances can act as an agonist at certain receptors and as an antagonist at others. Such a substance is called an agonist-antagonist. Understanding the differences between agonists and antagonists is crucial in drug development and treatment.

Compared to other antidepressants, agomelatine has a lower likelihood of causing sexual dysfunction. This is because other antidepressants can cause various changes in the body, such as sedation, hormonal changes, and disruption of the cholinergic/adrenergic balance, which can lead to sexual dysfunction. Additionally, other antidepressants may inhibit nitric oxide and increase neurotransmission, which can also contribute to sexual dysfunction. However, agomelatine does not act through the serotonergic of alpha adrenergic systems and has a lower propensity for causing these changes, resulting in less sexual dysfunction.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

Antipsychotic drugs such as chlorpromazine have an antidopaminergic effect, which can lead to hyperprolactinemia and hypogonadism. Additionally, they can cause a serious condition called neuroleptic malignant syndrome, which is characterized by hyperthermia, muscular rigidity, and altered consciousness. This syndrome is caused by the blocking of dopamine receptors and is more commonly associated with typical antipsychotics like chlorpromazine, haloperidol, and trifluoperazine. However, cases have also been reported with most atypical antipsychotic agents.

Antipsychotic drugs are known to cause weight gain, but some more than others. The reason for this is not due to a direct metabolic effect, but rather an increase in appetite and a decrease in activity levels. The risk of weight gain appears to be linked to clinical response. There are several suggested mechanisms for this, including antagonism of certain receptors and hormones that stimulate appetite. The risk of weight gain varies among different antipsychotics, with clozapine and olanzapine having the highest risk. Management strategies for antipsychotic-induced weight gain include calorie restriction, low glycemic index diet, exercise, and switching to an alternative antipsychotic. Aripiprazole, ziprasidone, and lurasidone are recommended as alternative options. Other options include aripiprazole augmentation, metformin, orlistat, liraglutide, and topiramate.

Most antidepressants and stimulants target monoamine transporters, which are crucial molecular targets. These transporters are also targeted by 30% of all psychotropic drugs. Another 30% of psychotropic drugs target G-protein-linked receptors, while enzymes are targeted by about 10% of these drugs. Monoamine oxidase inhibitors (MAOIs) are a type of antidepressant that targets the enzyme monoamine oxidase. Ligand-gated and voltage-gated ion channels are targeted by 20% and 10% of all psychotropic drugs, respectively.

Nitrous oxide functions as a vasodilator during penile erection by diffusing through the muscle cell membrane and binding to guanylyl cyclase. This enzyme catalyzes the conversion of GTP to cyclic GMP, which activates a cGMP-dependent protein kinase. This kinase stimulates the uptake of calcium by the endoplasmic reticulum of the muscle cell, leading to muscle relaxation and vasodilation, resulting in an erection.

To end the erection, cGMP is converted into GMP by a specific phosphodiesterase (PDE). There are ten families of PDEs, with PDE5 being the primary PDE found in vascular smooth muscle. Sildenafil (Viagra) is a specific inhibitor of PDE5, blocking the breakdown of cGMP and prolonging the effects of cGMP, thereby prolonging the erection.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Antidepressants: Minimum Effective Doses

According to the Maudsley 13th, the following are the minimum effective doses for various antidepressants:

– Citalopram: 20 mg/day
– Fluoxetine: 20 mg/day
– Fluvoxamine: 50 mg/day
– Paroxetine: 20 mg/day
– Sertraline: 50 mg/day
– Mirtazapine: 30 mg/day
– Venlafaxine: 75 mg/day
– Duloxetine: 60 mg/day
– Agomelatine: 25 mg/day
– Moclobemide: 300 mg/day
– Trazodone: 150 mg/day

Note that these are minimum effective doses and may vary depending on individual factors and response to treatment. It is important to consult with a healthcare professional before starting of changing any medication regimen.

Agomelatine acts as a melatonin receptor agonist and a selective antagonist of serotonin receptors, without affecting the uptake of serotonin, noradrenaline, of dopamine. Second-generation antipsychotics exhibit some level of dopamine D2 antagonism. Mirtazapine functions as a presynaptic antagonist of alpha-2 adrenoceptors. Reboxetine selectively inhibits the reuptake of noradrenaline. Venlafaxine and duloxetine are recognized as inhibitors of serotonin and noradrenaline reuptake.

Blurred vision occurs as a result of muscarinic blockade, which causes the pupils to dilate (mydriasis).

Receptors and Side-Effects

Histamine H1 Blockade:
– Weight gain
– Sedation

Alpha 1 Blockade:
– Orthostatic hypotension
– Sedation
– Sexual dysfunction
– Priapism

Muscarinic Central M1 Blockade:
– Agitation
– Delirium
– Memory impairment
– Confusion
– Seizures

Muscarinic Peripheral M1 Blockade:
– Dry mouth
– Ataxia
– Blurred vision
– Narrow angle glaucoma
– Constipation
– Urinary retention
– Tachycardia

Each receptor has specific effects on the body, but they can also have side-effects. Histamine H1 blockade can cause weight gain and sedation. Alpha 1 blockade can lead to orthostatic hypotension, sedation, sexual dysfunction, and priapism. Muscarinic central M1 blockade can cause agitation, delirium, memory impairment, confusion, and seizures. Muscarinic peripheral M1 blockade can result in dry mouth, ataxia, blurred vision, narrow angle glaucoma, constipation, urinary retention, and tachycardia. It is important to be aware of these potential side-effects when using medications that affect these receptors.

Mechanisms of action for illicit drugs can be classified based on their effects on ionotropic receptors of ion channels, G coupled receptors, of monoamine transporters. Cocaine and amphetamine both increase dopamine levels in the synaptic cleft, but through different mechanisms. Cocaine directly blocks the dopamine transporter, while amphetamine binds to the transporter and increases dopamine efflux through various mechanisms, including inhibition of vesicular monoamine transporter 2 and monoamine oxidase, and stimulation of the intracellular receptor TAAR1. These mechanisms result in increased dopamine levels in the synaptic cleft and reuptake inhibition.

The liver plays a significant role in breaking down clozapine through the action of CYP450 enzymes, with CYP1A2, CYP3A4, and CYP2D6 being particularly involved in the process.

The Cytochrome P450 system is a group of enzymes that metabolize drugs by altering their functional groups. The system is located in the liver and small intestine and is involved in drug interactions through enzyme induction of inhibition. Notable inducers include smoking, alcohol, and St John’s Wort, while notable inhibitors include grapefruit juice and some SSRIs. CYP2D6 is important due to genetic polymorphism, and CYP3A4 is the most abundant subfamily and is commonly involved in interactions. Grapefruit juice inhibits both CYP1A2 and CYP3A4, while tobacco smoking induces CYP1A2. The table summarizes the main substrates, inhibitors, and inducers for each CYP enzyme.

Antidepressants can cause discontinuation symptoms when patients stop taking them, regardless of the type of antidepressant. These symptoms usually occur within 5 days of stopping the medication and can last up to 3 weeks. Symptoms include flu-like symptoms, dizziness, insomnia, vivid dreams, irritability, crying spells, and sensory symptoms. SSRIs and related drugs with short half-lives, such as paroxetine and venlafaxine, are particularly associated with discontinuation symptoms. Tapering antidepressants at the end of treatment is recommended to prevent these symptoms. TCAs and MAOIs are also associated with discontinuation symptoms, with amitriptyline and imipramine being the most common TCAs and all MAOIs being associated with prominent discontinuation symptoms. Patients at highest risk for discontinuation symptoms include those on antidepressants with shorter half-lives, those who have been taking antidepressants for 8 weeks of longer, those using higher doses, younger people, and those who have experienced discontinuation symptoms before. Agomelatine is not associated with any discontinuation syndrome. If a discontinuation reaction occurs, restarting the antidepressant of switching to an alternative with a longer half-life and tapering more slowly may be necessary. Explanation and reassurance are often sufficient for mild symptoms. These guidelines are based on the Maudsley Guidelines 14th Edition and a study by Tint (2008).

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

The exact reason for the development of polyuria and polydipsia (nephrogenic diabetes insipidus) as a side effect of lithium treatment is not fully understood, but it is believed to be linked to the impact of lithium on ion transportation.

Agomelatine acts as a melatonergic agonist at MT1 and MT2 receptors and also as a 5-HT2C antagonist, indirectly increasing norepinephrine and dopamine levels to alleviate depression. Moclobemide, an MAO-A inhibitor, boosts serotonin, dopamine, and norepinephrine levels in the brain, resulting in antidepressant effects. Fluoxetine, a selective serotonin reuptake inhibitor, elevates serotonin levels, while venlafaxine, a serotonin and norepinephrine reuptake inhibitor, enhances the concentration of both chemicals in the brain, leading to antidepressant benefits.

This is a case of neuroleptic malignant syndrome, which is primarily associated with the use of antipsychotic medications. The key features of NMS include mental status changes, muscular rigidity, hyperthermia, and autonomic instability, typically presenting as tachycardia. Mental state changes are often the first symptom to appear.

Serotonin Syndrome and Neuroleptic Malignant Syndrome are two conditions that can be difficult to differentiate. Serotonin Syndrome is caused by excess serotonergic activity in the CNS and is characterized by neuromuscular abnormalities, altered mental state, and autonomic dysfunction. On the other hand, Neuroleptic Malignant Syndrome is a rare acute disorder of thermoregulation and neuromotor control that is almost exclusively caused by antipsychotics. The symptoms of both syndromes can overlap, but there are some distinguishing clinical features. Hyper-reflexia, ocular clonus, and tremors are more prominent in Serotonin Syndrome, while Neuroleptic Malignant Syndrome is characterized by uniform ‘lead-pipe’ rigidity and hyporeflexia. Symptoms of Serotonin Syndrome usually resolve within a few days of stopping the medication, while Neuroleptic Malignant Syndrome can take up to 14 days to remit with appropriate treatment. The following table provides a useful guide to the main differentials of Serotonin Syndrome and Neuroleptic Malignant Syndrome.

The time course of drug concentration in various body parts is described and predicted by pharmacokinetics, while pharmacodynamics is used to describe the intensity and time course of a drug’s effects. Pharmacological actions encompass genetic and environmental factors that affect an individual’s response to and tolerance of psychotropic agents. The mechanism of drugs’ therapeutic effects is described as how they are produced.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

Hyponatremia is commonly linked to the use of SSRIs (antidepressants) and typical antipsychotics.

Hyponatremia in Psychiatric Patients

Hyponatremia, of low serum sodium, can occur in psychiatric patients due to the disorder itself, its treatment, of other medical conditions. Symptoms include nausea, confusion, seizures, and muscular cramps. Drug-induced hyponatremia is known as the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH), which results from excessive secretion of ADH and fluid overload. Diagnosis is based on clinically euvolemic state with low serum sodium and osmolality, raised urine sodium and osmolality. SSRIs, SNRIs, and tricyclics are the most common drugs that can cause SIADH. Risk factors for SIADH include starting a new drug, and treatment usually involves fluid restriction and sometimes demeclocycline.

While there is some conflicting evidence, it is generally believed that tobacco smoking does not have a significant impact on the effectiveness of lithium.

Tobacco products predominantly smoked tobacco that burns the organic matter produces hydrocarbons. And these hydrocarbons lead to the induction of certain cytochrome p450 enzymes notably CYP1A2 predominantly but also CYP1A1 and also CYP2E1 or other major enzymes that are induced by tobacco. This will lead to the increased clearance of a variety of pharmacologic agents that are used especially in psychiatric populations. The most important ones to remember are antipsychotics and one of the antidepressants specifically fluvoxamine. When it comes to antipsychotics, clozapine and olanzapine are probably the most important ones to remember but also haloperidol and chlorpromazine could be affected as well. But for antidepressants, it’s really fluvoxamine that’s going to be mostly affected. And what this means is that while the person is actively smoking cigarettes, the clearance of these medications is increased probably anywhere from 20% to 50% or sometimes even more. And so what this means is those individuals may require higher doses than usual.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Tricyclic Antidepressants: Uses, Types, and Side-Effects

Tricyclic antidepressants (TCAs) are a type of medication used for depression and neuropathic pain. However, due to their side-effects and toxicity in overdose, they are not commonly used for depression anymore. TCAs can be divided into two types: first generation (tertiary amines) and second generation (secondary amines). The secondary amines have a lower side effect profile and act primarily on noradrenaline, while the tertiary amines boost serotonin and noradrenaline.

Some examples of secondary amines include desipramine, nortriptyline, protriptyline, and amoxapine. Examples of tertiary amines include amitriptyline, lofepramine, imipramine, clomipramine, dosulepin (dothiepin), doxepin, trimipramine, and butriptyline. Common side-effects of TCAs include drowsiness, dry mouth, blurred vision, constipation, and urinary retention.

Low-dose amitriptyline is commonly used for neuropathic pain and prophylaxis of headache. Lofepramine has a lower incidence of toxicity in overdose. However, amitriptyline and dosulepin (dothiepin) are considered the most dangerous in overdose. It is important to consult with a healthcare provider before taking any medication and to follow their instructions carefully.

Clomipramine as a Second-Line Treatment for OCD

Paragraph: Clomipramine is a tricyclic antidepressant (TCA) that has a high affinity for serotonin receptors, making it the most serotonergic TCA. The National Institute for Health and Care Excellence (NICE) guidelines recommend clomipramine as a second-line treatment for obsessive-compulsive disorder (OCD). However, patients may find antimuscarinic side effects, such as dry mouth and constipation, difficult to tolerate. It is worth noting that using TCAs for nerve and chronic pain is not an approved indication.

Sertraline and other selective serotonin reuptake inhibitors (SSRIs) are effective in treating paraphilias by reducing libido and delaying orgasm. While all serotonergic antidepressants have sexual effects, they are most common with SSRIs. Although these effects are typically considered side effects, they can be beneficial in treating paraphilias.

Sexual side effects are prevalent with many antidepressants, with SSRIs having the highest incidence at 60-70%. Venlafaxine has a 70% incidence, duloxetine has a 46% incidence, monoamine oxidase inhibitors (MAOIs) have a 40% incidence, tricyclic antidepressants (TCAs) have a 30% incidence (but are more common with clomipramine), mirtazapine has a 25% incidence, reboxetine has a 5-10% incidence, and the incidence with trazodone is unknown.

Cyproterone acetate (Androcur) is an effective treatment for hypersexuality as an anti-androgen that reduces testosterone to pre-pubescent levels. These findings are based on the Maudsley Guidelines, 11th edition, page 210.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

In certain cases, the addition of 5-10 mg of aripiprazole has demonstrated the ability to restore hyperprolactinaemia to normal levels.

Antipsychotics and Sexual Dysfunction: Causes, Risks, and Management

Sexual dysfunction is a common side effect of antipsychotic medication, with the highest risk associated with risperidone and haloperidol due to their effect on prolactin levels. Clozapine, olanzapine, quetiapine, aripiprazole, asenapine, and lurasidone are associated with lower rates of sexual dysfunction. The Arizona Sexual Experiences Scale (ASEX) can be used to measure sexual dysfunction before and during treatment. Management options include excluding other causes, watchful waiting, dose reduction, switching to a lower risk agent, adding aripiprazole, considering an antidote medication, of using sildenafil for erectile dysfunction. It is important to address sexual dysfunction to improve quality of life and medication adherence.

The ‘cheese reaction’ is a potential adverse effect of phenelzine, a type of medication known as a monoamine oxidase inhibitor (MAOI). When a person takes phenelzine, foods that contain high levels of tyramine are not broken down properly due to the inhibition of MAO. This causes tyramine to enter the bloodstream and trigger the release of noradrenaline, which can lead to dangerous spikes in blood pressure.

The term ‘cheese reaction’ comes from the fact that many types of cheese are particularly high in tyramine. While early MAOIs irreversibly inhibit monoamine oxidase, newer medications like moclobemide are reversible and considered to be safer.

Both lithium carbonate and citrate are used for the treatment and prevention of various mental health conditions, including mania, bipolar disorder, recurrent depression, and aggressive of self-harming behavior. Lithium carbonate is available in tablet form, while lithium citrate is a liquid medication.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Toxicity in Overdose: Comparing MAOIs, SSRIs, Tricyclics, and Mirtazapine

When it comes to the risk of overdose, not all antidepressants are created equal. MAOIs (except for moclobemide) have a high toxicity level, with as little as 400 mg of phenelzine being potentially fatal. On the other hand, SSRIs are considered relatively safe in overdose. Tricyclics, except for lofepramine, have a higher risk of toxicity in overdose. However, lofepramine is relatively safe in overdose. Mirtazapine, while sedative, has a low risk of toxicity even in large doses, and may not produce any symptoms. It’s important to note that regardless of the perceived safety of a medication, any overdose should be taken seriously and medical attention should be sought immediately.

The biological response to a drug can only be triggered by the portion of the drug that is not bound.

Drug Distribution in the Body

After being absorbed, drugs can distribute to different parts of the body, such as fat, plasma, muscle, brain tissue, and glands like the thyroid. However, for a drug to have an effect, it must be present in the plasma in an unbound state. This means that the drug molecules are not attached to any other molecules and are free to interact with their target receptors. The concentration of unbound drug in the plasma is what determines the drug’s effectiveness and potential side effects. Therefore, understanding a drug’s distribution in the body is crucial for determining the appropriate dosage and monitoring its effects.

Lithium has a tendency to remain unattached to proteins and instead remains unbound within the body, resulting in its efficient elimination from the bloodstream through haemodialysis.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Flumazenil: A Selective GABAA Receptor Antagonist

Flumazenil is a medication that selectively blocks the effects of benzodiazepines on the GABAA receptor. It is used to reverse the sedative effects caused by benzodiazepines, either partially or completely. Flumazenil works by competitively interacting with benzodiazepine receptors, which can reverse the binding of benzodiazepines to these receptors. It is administered intravenously and has a short half-life of about 60 minutes. The effects of flumazenil are usually shorter than those of benzodiazepines, and sedation may recur. Flumazenil also blocks non-benzodiazepine-agonists like zopiclone. However, it has no effect on other drugs such as barbiturates, ethanol, of other GABA-mimetic agents unless they act on the benzodiazepine receptor site. The hypnosedative effects of benzodiazepines are rapidly blocked within 1-2 minutes after intravenous administration, and the duration of action ranges from 20 to 50 minutes.

ADHD medications can be classified into stimulant and non-stimulant drugs. The therapeutic effects of these drugs are believed to be mediated through the action of noradrenaline in the prefrontal cortex. Common side effects of these drugs include decreased appetite, insomnia, nervousness, headache, and nausea. Stimulant drugs like dexamphetamine, methylphenidate, and lisdexamfetamine inhibit the reuptake of dopamine and noradrenaline. Non-stimulant drugs like atomoxetine, guanfacine, and clonidine work by increasing noradrenaline levels in the synaptic cleft through different mechanisms. The most common side effects of these drugs are decreased appetite, somnolence, headache, and abdominal pain.

The combination of the patient’s symptoms and medical history strongly suggests the presence of neuromuscular malignant syndrome. To confirm the diagnosis, a serum creatine kinase test would be the most beneficial investigation to conduct. Although creatine kinase is a highly sensitive marker for muscle tissue damage, it is not specific to this condition and may also be elevated in other conditions such as acute alcohol intoxication of acute psychosis.

Serotonin Syndrome and Neuroleptic Malignant Syndrome are two conditions that can be difficult to differentiate. Serotonin Syndrome is caused by excess serotonergic activity in the CNS and is characterized by neuromuscular abnormalities, altered mental state, and autonomic dysfunction. On the other hand, Neuroleptic Malignant Syndrome is a rare acute disorder of thermoregulation and neuromotor control that is almost exclusively caused by antipsychotics. The symptoms of both syndromes can overlap, but there are some distinguishing clinical features. Hyper-reflexia, ocular clonus, and tremors are more prominent in Serotonin Syndrome, while Neuroleptic Malignant Syndrome is characterized by uniform ‘lead-pipe’ rigidity and hyporeflexia. Symptoms of Serotonin Syndrome usually resolve within a few days of stopping the medication, while Neuroleptic Malignant Syndrome can take up to 14 days to remit with appropriate treatment. The following table provides a useful guide to the main differentials of Serotonin Syndrome and Neuroleptic Malignant Syndrome.

Antipsychotics: Common Side Effects and Relative Adverse Effects

Antipsychotics are medications used to treat various mental health conditions, including schizophrenia and bipolar disorder. However, they can also cause side effects that can be bothersome of even serious. The most common side effects of antipsychotics are listed in the table below, which includes the adverse effects associated with their receptor activity.

Antidopaminergic effects: These effects are related to the medication’s ability to block dopamine receptors in the brain. They can cause galactorrhoea, gynecomastia, menstrual disturbance, lowered sperm count, reduced libido, Parkinsonism, dystonia, akathisia, and tardive dyskinesia.

Anticholinergic effects: These effects are related to the medication’s ability to block acetylcholine receptors in the brain. They can cause dry mouth, blurred vision, urinary retention, and constipation.

Antiadrenergic effects: These effects are related to the medication’s ability to block adrenaline receptors in the body. They can cause postural hypotension and ejaculatory failure.

Histaminergic effects: These effects are related to the medication’s ability to block histamine receptors in the brain. They can cause drowsiness.

The Maudsley Guidelines provide a rough guide to the relative adverse effects of different antipsychotics. The table below summarizes their findings, with +++ indicating a high incidence of adverse effects, ++ indicating a moderate incidence, + indicating a low incidence, and – indicating a very low incidence.

Drug Sedation Weight gain Diabetes EPSE Anticholinergic Postural Hypotension Prolactin elevation
Amisulpride – + + + – – +++
Aripiprazole – +/- – +/- – – –
Asenapine + + +/- +/- – – +/-
Clozapine +++ +++ +++ – +++ +++ –
Flupentixol + ++ + ++ ++ + +++
Fluphenazine + + + +++ ++ + +++
Haloperidol + + +/- +++ + + +++
Olanzapine ++ +++ +++ +/- + + +
Paliperidone + ++ + + + ++ +++
Pimozide + + – + + + +++
Quetiapine ++ ++ ++ – + ++ –
Risperidone + ++ + + + ++ +++
Zuclopenthixol ++ ++ + ++ ++ + +++

Overall, it is important to discuss the potential side effects of antipsychotics with a healthcare provider and to monitor for any adverse effects while taking these medications.

Lisinopril is a medication that belongs to the class of ACE inhibitors and is commonly prescribed to treat hypertension and heart failure.

Hyponatremia in Psychiatric Patients

Hyponatremia, of low serum sodium, can occur in psychiatric patients due to the disorder itself, its treatment, of other medical conditions. Symptoms include nausea, confusion, seizures, and muscular cramps. Drug-induced hyponatremia is known as the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH), which results from excessive secretion of ADH and fluid overload. Diagnosis is based on clinically euvolaemic state with low serum sodium and osmolality, raised urine sodium and osmolality. SSRIs, SNRIs, and tricyclics are the most common drugs that can cause SIADH. Risk factors for SIADH include starting a new drug, and treatment usually involves fluid restriction and sometimes demeclocycline.

SNRIs include duloxetine and venlafaxine.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Elevated levels of creatine phosphokinase (CPK) are observed in NMS.

Serotonin Syndrome and Neuroleptic Malignant Syndrome are two conditions that can be difficult to differentiate. Serotonin Syndrome is caused by excess serotonergic activity in the CNS and is characterized by neuromuscular abnormalities, altered mental state, and autonomic dysfunction. On the other hand, Neuroleptic Malignant Syndrome is a rare acute disorder of thermoregulation and neuromotor control that is almost exclusively caused by antipsychotics. The symptoms of both syndromes can overlap, but there are some distinguishing clinical features. Hyper-reflexia, ocular clonus, and tremors are more prominent in Serotonin Syndrome, while Neuroleptic Malignant Syndrome is characterized by uniform ‘lead-pipe’ rigidity and hyporeflexia. Symptoms of Serotonin Syndrome usually resolve within a few days of stopping the medication, while Neuroleptic Malignant Syndrome can take up to 14 days to remit with appropriate treatment. The following table provides a useful guide to the main differentials of Serotonin Syndrome and Neuroleptic Malignant Syndrome.

The Cytochrome P450 system is a group of enzymes that metabolize drugs by altering their functional groups. The system is located in the liver and small intestine and is involved in drug interactions through enzyme induction of inhibition. Notable inducers include smoking, alcohol, and St John’s Wort, while notable inhibitors include grapefruit juice and some SSRIs. CYP2D6 is important due to genetic polymorphism, and CYP3A4 is the most abundant subfamily and is commonly involved in interactions. Grapefruit juice inhibits both CYP1A2 and CYP3A4, while tobacco smoking induces CYP1A2. The table summarizes the main substrates, inhibitors, and inducers for each CYP enzyme.

Antidepressants can cause sexual dysfunction as a side-effect, although the rates vary. The impact on sexual desire, arousal, and orgasm can differ depending on the type of antidepressant. It is important to rule out other causes and consider non-pharmacological strategies such as reducing the dosage of taking drug holidays. If necessary, switching to a lower risk antidepressant of using pharmacological options such as phosphodiesterase inhibitors of mirtazapine augmentation can be considered. The Maudsley Guidelines 14th Edition provides a helpful table outlining the risk of sexual dysfunction for different antidepressants.

Out of the given options, amisulpride is the most suitable medication as it is not extensively metabolized by the liver. However, it should be avoided in individuals with established renal failure as a normal glomerular filtration rate is considered to be >90 ml/min/1.73m2.

Hepatic Impairment: Recommended Drugs

Patients with hepatic impairment may experience reduced ability to metabolize drugs, toxicity, enhanced dose-related side effects, reduced ability to synthesize plasma proteins, and elevated levels of drugs subject to first-pass metabolism due to reduced hepatic blood flow. The Maudsley Guidelines 14th Ed recommends the following drugs for patients with hepatic impairment:

Antipsychotics: Paliperidone (if depot required), Amisulpride, Sulpiride

Antidepressants: Sertraline, Citalopram, Paroxetine, Vortioxetine (avoid TCA and MAOI)

Mood stabilizers: Lithium

Sedatives: Lorazepam, Oxazepam, Temazepam, Zopiclone 3.75mg (with care)

, coma, respiratory depression (rare)

According to the Maudsley Guidelines, haloperidol causes the greatest increase in QTc interval among antipsychotic medications. It is important for men to have a QTc interval below 440 ms and women below 470 ms. While aripiprazole and paliperidone have not been proven to cause an increase in QTc interval, other antipsychotics, including atypical drugs like quetiapine, can have moderate to significant effects. A prolonged QTc interval, especially above 500ms, is associated with sudden cardiac death. Diazepam and other benzodiazepines have no effect on QTc interval, while amisulpride has a low effect. Citalopram is the only SSRI that has a low effect on QTc interval. Although erythromycin and other antibiotics can have an effect on QTc interval, the question specifically asks about psychotropic medications.

Antipsychotics are commonly used to treat various mental health conditions. Most atypical antipsychotics require twice daily administration due to their short half-lives, except for olanzapine, aripiprazole, and risperidone. These medications have longer half-lives and can be administered once daily. A recent randomized controlled trial compared once versus twice daily dosing of risperidone and olanzapine and found no significant difference in effectiveness and efficacy outcomes. However, the study suggests that once-daily dosing may be preferable due to lower mean dose and better side effect profile, especially for olanzapine.

Although only gluteal injection is approved for olanzapine, deltoid injection is not as effective. Smoking and carbamazepine can induce the metabolism of olanzapine, resulting in lower concentrations. However, the increase in olanzapine clearance is only slight to moderate, and the clinical implications are likely limited. Clinical monitoring is recommended, and an increase in olanzapine dosage may be necessary. While test doses are not required for olanzapine embonate, the Summary of Product Characteristics (SPC) recommends treating patients with oral olanzapine before administering ZYPADHERA to establish tolerability and response.

, coma, respiratory depression (rare)

There is no active metabolite produced by lithium.

The Significance of Active Metabolites in Drug Discovery and Development

Certain drugs are classified as prodrugs, which means that they are inactive when administered and require metabolism to become active. These drugs are converted into an active form, which is referred to as an active metabolite. Some drugs have important active metabolites, such as diazepam, dothiepin, fluoxetine, imipramine, risperidone, amitriptyline, and codeine, which are desmethyldiazepam, dothiepin sulfoxide, norfluoxetine, desipramine, 9-hydroxyrisperidone, nortriptyline, and morphine, respectively.

The role of pharmacologically active metabolites in drug discovery and development is significant. Understanding the active metabolites of a drug can help in the development of more effective and safer drugs. Active metabolites can also provide insights into the pharmacokinetics and pharmacodynamics of a drug, which can aid in the optimization of dosing regimens. Additionally, active metabolites can have different pharmacological properties than the parent drug, which can lead to the discovery of new therapeutic uses for a drug. Therefore, the study of active metabolites is an important aspect of drug discovery and development.

Aripiprazole does not affect the QTc interval and has minimal risk of extrapyramidal side effects, sedation, of weight gain. Amisulpride, citalopram, and quetiapine have a moderate effect on the QTc interval, which requires ECG monitoring due to a prolongation of >10 msec. Haloperidol has a high effect on the QTc interval, which mandates ECG monitoring due to a prolongation of >20 msec.

EPSE’s have been linked to the use of fluoxetine, and all of the treatment options are utilized to address them.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

The half-life of a drug is the time taken for its concentration to fall to one half of its value. Drugs with long half-lives may require a loading dose to achieve therapeutic plasma concentrations rapidly. It takes about 4.5 half-lives to reach steady state plasma levels. Most drugs follow first order kinetics, where a constant fraction of the drug in the body is eliminated per unit time. However, some drugs may follow zero order kinetics, where the plasma concentration of the drug decreases at a constant rate, despite the concentration of the drug. For drugs with nonlinear kinetics of dose-dependent kinetics, the relationship between the AUC of CSS and dose is not linear, and the kinetic parameters may vary depending on the administered dose.

This question is quite challenging, and it’s understandable if you didn’t get the answer right. Even healthcare professionals like consultants and pharmacists may struggle with this. However, for the record, the levels of lamotrigine can be increased by sertraline and valproate.

Lamotrigine: An Anticonvulsant Drug for Epilepsy, Bipolar Disorder, and Depression

Lamotrigine is a medication that belongs to the class of anticonvulsants. It is commonly used in the treatment of epilepsy, bipolar disorder, and depression. Epilepsy is a neurological disorder characterized by recurrent seizures, while bipolar disorder is a mental illness that causes extreme mood swings. Depression, on the other hand, is a mood disorder that affects a person’s thoughts, feelings, and behavior.

Lamotrigine works by stabilizing the electrical activity in the brain, which helps to prevent seizures and mood swings. It is often used as a first-line treatment for epilepsy and is effective in reducing the frequency and severity of seizures. In bipolar disorder, lamotrigine is used to prevent episodes of mania and depression. It can also be used as an add-on therapy for depression, particularly in cases where other antidepressants have not been effective.

Overall, lamotrigine is a versatile medication that can be used to treat a range of neurological and psychiatric conditions. It is generally well-tolerated and has few side effects, making it a popular choice for many patients. However, as with all medications, it is important to discuss the risks and benefits with your healthcare provider before starting treatment.

Although the occurrence of the post-injection syndrome is rare, patients must still be observed for three hours after receiving the depot injection.

, coma, respiratory depression (rare)

Bupropion inhibits the reuptake of noradrenaline and dopamine, making it an NDRI.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

For individuals with hepatic impairment, it is advisable to use low dose haloperidol. Amisulpride and paliperidone are eliminated through the kidneys, but there is no clinical data to support their safety in this population. Aripiprazole, olanzapine, quetiapine, and risperidone undergo significant liver metabolism. Chlorpromazine has a high potential for liver toxicity. Clozapine should not be used in individuals with active liver disease.

Pharmacological management of dementia involves the use of acetylcholinesterase inhibitors (AChE inhibitors) and memantine. AChE inhibitors prevent the breakdown of acetylcholine, which is deficient in Alzheimer’s due to the loss of cholinergic neurons. Donepezil, galantamine, and rivastigmine are commonly used AChE inhibitors in the management of Alzheimer’s. However, gastrointestinal side effects such as nausea and vomiting are common with these drugs.

Memantine, on the other hand, is an NMDA receptor antagonist that blocks the effects of pathologically elevated levels of glutamate that may lead to neuronal dysfunction. It has a half-life of 60-100 hours and is primarily renally eliminated. Common adverse effects of memantine include somnolence, dizziness, hypertension, dyspnea, constipation, headache, and elevated liver function tests.

Overall, pharmacological management of dementia aims to improve cognitive function and slow down the progression of the disease. However, it is important to note that these drugs do not cure dementia and may only provide temporary relief of symptoms.

Antidepressants and Diabetes

Depression is a prevalent condition among patients with diabetes. It is crucial to select the appropriate antidepressant as some may have negative effects on weight and glucose levels. The first-line treatment for depression in diabetic patients is selective serotonin reuptake inhibitors (SSRIs), with fluoxetine having the most supporting data. Serotonin-norepinephrine reuptake inhibitors (SNRIs) are also likely to be safe, but there is less evidence to support their use. Tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs) should be avoided. These recommendations are based on the Maudsley Guidelines 10th Edition.

Discontinuation syndrome of selective serotonin reuptake inhibitors may manifest with diverse symptoms such as abdominal pain, vomiting, and diarrhea.

Antidepressants can cause discontinuation symptoms when patients stop taking them, regardless of the type of antidepressant. These symptoms usually occur within 5 days of stopping the medication and can last up to 3 weeks. Symptoms include flu-like symptoms, dizziness, insomnia, vivid dreams, irritability, crying spells, and sensory symptoms. SSRIs and related drugs with short half-lives, such as paroxetine and venlafaxine, are particularly associated with discontinuation symptoms. Tapering antidepressants at the end of treatment is recommended to prevent these symptoms. TCAs and MAOIs are also associated with discontinuation symptoms, with amitriptyline and imipramine being the most common TCAs and all MAOIs being associated with prominent discontinuation symptoms. Patients at highest risk for discontinuation symptoms include those on antidepressants with shorter half-lives, those who have been taking antidepressants for 8 weeks of longer, those using higher doses, younger people, and those who have experienced discontinuation symptoms before. Agomelatine is not associated with any discontinuation syndrome. If a discontinuation reaction occurs, restarting the antidepressant of switching to an alternative with a longer half-life and tapering more slowly may be necessary. Explanation and reassurance are often sufficient for mild symptoms. These guidelines are based on the Maudsley Guidelines 14th Edition and a study by Tint (2008).

Alternative Routes of Administration for Antidepressants

While most antidepressants are taken orally, there are a few alternative routes of administration available. However, it is important to note that these non-oral preparations should only be used when absolutely necessary, as they may not have a UK licence.

One effective alternative route is sublingual administration of fluoxetine liquid. Buccal administration of selegiline is also available. Crushed amitriptyline has been shown to be effective when administered via this route.

Intravenous administration is another option, with several antidepressants available in IV preparations, including citalopram, escitalopram, mirtazapine, amitriptyline, clomipramine, and allopregnanolone (which is licensed in the US for postpartum depression). Ketamine has also been shown to be effective when administered intravenously.

Intramuscular administration of flupentixol has been shown to have a mood elevating effect, but amitriptyline was discontinued as an IM preparation due to the high volumes required.

Transdermal administration of selegiline is available, and suppositories containing amitriptyline, clomipramine, imipramine, and trazodone have been manufactured by pharmacies, although there is no clear data on their effectiveness. Sertraline tablets and doxepin capsules have also been given rectally.

Compared to other SSRIs, paroxetine has a higher affinity for muscarinic acetylcholine receptors, resulting in greater sedation. Conversely, citalopram and escitalopram have a low likelihood of causing sedation. Fluoxetine and sertraline do not typically induce sedation.

Headache is a very common symptom, while agitation and fatigue are also frequently reported. Bradycardia is less commonly observed. Extrapyramidal symptoms are rare occurrences.

Pharmacological management of dementia involves the use of acetylcholinesterase inhibitors (AChE inhibitors) and memantine. AChE inhibitors prevent the breakdown of acetylcholine, which is deficient in Alzheimer’s due to the loss of cholinergic neurons. Donepezil, galantamine, and rivastigmine are commonly used AChE inhibitors in the management of Alzheimer’s. However, gastrointestinal side effects such as nausea and vomiting are common with these drugs.

Memantine, on the other hand, is an NMDA receptor antagonist that blocks the effects of pathologically elevated levels of glutamate that may lead to neuronal dysfunction. It has a half-life of 60-100 hours and is primarily renally eliminated. Common adverse effects of memantine include somnolence, dizziness, hypertension, dyspnea, constipation, headache, and elevated liver function tests.

Overall, pharmacological management of dementia aims to improve cognitive function and slow down the progression of the disease. However, it is important to note that these drugs do not cure dementia and may only provide temporary relief of symptoms.

Citalopram can moderately prolong QTc (>10 msec), while aripiprazole and paliperidone have no effect. Haloperidol and pimozide have a high effect, and quetiapine and amisulpride have a moderate effect. Clozapine, risperidone, and olanzapine have a low effect (<10 msec prolongation). Lamotrigine, mirtazapine, and SSRIs (excluding citalopram) do not have an effect on QTc interval.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Tricyclic Antidepressants: First and Second Generation

Tricyclic antidepressants are classified into two generations: first generation of tertiary amines, and second generation of secondary amines. The secondary amines are known to have fewer side effects and primarily affect noradrenaline, while the tertiary amines are believed to enhance both serotonin and noradrenaline.

Secondary amines include Desipramine, Nortriptyline, Protriptyline, and Amoxapine. On the other hand, tertiary amines include Amitriptyline, Lofepramine, Imipramine, Clomipramine, Dosulepin (Dothiepin), Doxepin, Trimipramine, and Butriptyline.

By understanding the differences between the two generations of tricyclic antidepressants, healthcare professionals can better tailor their treatment plans to their patients’ needs.

Antidepressants and Their Cardiac Effects

SSRIs are generally recommended for patients with cardiac disease as they may protect against myocardial infarction (MI). Untreated depression worsens prognosis in cardiovascular disease. Post MI, SSRIs and mirtazapine have either a neutral of beneficial effect on mortality. Sertraline is recommended post MI, but other SSRIs and mirtazapine are also likely to be safe. However, citalopram is associated with Torsades de pointes (mainly in overdose). Bupropion, citalopram, escitalopram, moclobemide, lofepramine, and venlafaxine should be used with caution of avoided in those at risk of serious arrhythmia (those with heart failure, left ventricular hypertrophy, previous arrhythmia, of MI).

Tricyclic antidepressants (TCAs) have established arrhythmogenic activity which arises as a result of potent blockade of cardiac sodium channels and variable activity at potassium channels. ECG changes produced include PR, QRS, and QT prolongation and the Brugada syndrome. Lofepramine is less cardiotoxic than other TCAs and seems to lack the overdose arrhythmogenicity of other TCAs. QT changes are not usually seen at normal clinical doses of antidepressants (but can occur, particularly with citalopram/escitalopram). The arrhythmogenic potential of TCAs and other antidepressants is dose-related.

Overall, SSRIs are recommended for patients with cardiac disease, while caution should be exercised when prescribing TCAs and other antidepressants, especially in those at risk of serious arrhythmia. It is important to monitor patients closely for any cardiac effects when prescribing antidepressants.

Antidepressants can cause discontinuation symptoms when patients stop taking them, regardless of the type of antidepressant. These symptoms usually occur within 5 days of stopping the medication and can last up to 3 weeks. Symptoms include flu-like symptoms, dizziness, insomnia, vivid dreams, irritability, crying spells, and sensory symptoms. SSRIs and related drugs with short half-lives, such as paroxetine and venlafaxine, are particularly associated with discontinuation symptoms. Tapering antidepressants at the end of treatment is recommended to prevent these symptoms. TCAs and MAOIs are also associated with discontinuation symptoms, with amitriptyline and imipramine being the most common TCAs and all MAOIs being associated with prominent discontinuation symptoms. Patients at highest risk for discontinuation symptoms include those on antidepressants with shorter half-lives, those who have been taking antidepressants for 8 weeks of longer, those using higher doses, younger people, and those who have experienced discontinuation symptoms before. Agomelatine is not associated with any discontinuation syndrome. If a discontinuation reaction occurs, restarting the antidepressant of switching to an alternative with a longer half-life and tapering more slowly may be necessary. Explanation and reassurance are often sufficient for mild symptoms. These guidelines are based on the Maudsley Guidelines 14th Edition and a study by Tint (2008).

Bupropion is classified as a noradrenaline dopamine reuptake inhibitor (NDRI) and functions by elevating the levels of neurotransmitters such as noradrenaline and dopamine. It has been utilized as an antidepressant and a smoking cessation aid.

Tricyclic Antidepressants: Uses, Types, and Side-Effects

Tricyclic antidepressants (TCAs) are a type of medication used for depression and neuropathic pain. However, due to their side-effects and toxicity in overdose, they are not commonly used for depression anymore. TCAs can be divided into two types: first generation (tertiary amines) and second generation (secondary amines). The secondary amines have a lower side effect profile and act primarily on noradrenaline, while the tertiary amines boost serotonin and noradrenaline.

Some examples of secondary amines include desipramine, nortriptyline, protriptyline, and amoxapine. Examples of tertiary amines include amitriptyline, lofepramine, imipramine, clomipramine, dosulepin (dothiepin), doxepin, trimipramine, and butriptyline. Common side-effects of TCAs include drowsiness, dry mouth, blurred vision, constipation, and urinary retention.

Low-dose amitriptyline is commonly used for neuropathic pain and prophylaxis of headache. Lofepramine has a lower incidence of toxicity in overdose. However, amitriptyline and dosulepin (dothiepin) are considered the most dangerous in overdose. It is important to consult with a healthcare provider before taking any medication and to follow their instructions carefully.

MAOIs: A Guide to Mechanism of Action, Adverse Effects, and Dietary Restrictions

First introduced in the 1950s, MAOIs were the first antidepressants introduced. However, they are not the first choice in treating mental health disorders due to several dietary restrictions and safety concerns. They are only a treatment option when all other medications are unsuccessful. MAOIs may be particularly useful in atypical depression (over eating / over sleeping, mood reactivity).

MAOIs block the monoamine oxidase enzyme, which breaks down different types of neurotransmitters from the brain: norepinephrine, serotonin, dopamine, as well as tyramine. There are two types of monoamine oxidase, A and B. The MOA A are mostly distributed in the placenta, gut, and liver, but MOA B is present in the brain, liver, and platelets. Selegiline and rasagiline are irreversible and selective inhibitors of MAO type B, but safinamide is a reversible and selective MAO B inhibitor.

The most common adverse effects of MAOIs occurring early in treatment are orthostatic hypotension, daytime sleepiness, insomnia, and nausea; later common effects include weight gain, muscle pain, myoclonus, paraesthesia, and sexual dysfunction.

Pharmacodynamic interactions with MAOIs can cause two types of problem: serotonin syndrome (mainly due to SSRIs) and elevated blood pressure (caused by indirectly acting sympathomimetic amines releasers, like pseudoephedrine and phenylephrine). The combination of MAOIs and some TCAs appears safe. Only those TCAs with significant serotonin reuptake inhibition (clomipramine and imipramine) are likely to increase the risk of serotonin syndrome.

Tyramine is a monoamine found in various foods, and is an indirect sympathomimetic that can cause a hypertensive reaction in patients receiving MAOI therapy. For this reason, dietary restrictions are required for patients receiving MAOIs. These restrictions include avoiding matured/aged cheese, fermented sausage, improperly stored meat, fava of broad bean pods, and certain drinks such as on-tap beer. Allowed foods include fresh cottage cheese, processed cheese slices, fresh packaged of processed meat, and other alcohol (no more than two bottled or canned beers of two standard glasses of wine, per day).

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Sedatives and Liver Disease

Sedatives are commonly used for their calming effects, but many of them are metabolized in the liver. Therefore, caution must be taken when administering sedatives to patients with liver disease. The Maudsley Guidelines recommend using low doses of the following sedatives in patients with hepatic impairment: lorazepam, oxazepam, temazepam, and zopiclone. It is important to note that zopiclone should also be used with caution and at low doses in this population. Proper management of sedative use in patients with liver disease can help prevent further damage to the liver and improve overall patient outcomes.

Charpentier synthesised Chlorpromazine in 1950, and it was subsequently introduced into clinical practice in the 1950s.

A Historical Note on the Development of Zimelidine, the First Selective Serotonin Reuptake Inhibitor

In 1960s, evidence began to emerge suggesting a significant role of serotonin in depression. This led to the development of zimelidine, the first selective serotonin reuptake inhibitor (SSRI). Zimelidine was derived from pheniramine and was marketed in Europe in 1982. However, it was removed from the market in 1983 due to severe side effects such as hypersensitivity reactions and Guillain-Barre syndrome.

Despite its short-lived availability, zimelidine paved the way for the development of other SSRIs such as fluoxetine, which was approved by the FDA in 1987 and launched in the US market in 1988 under the trade name Prozac. The development of SSRIs revolutionized the treatment of depression and other mood disorders, providing a safer and more effective alternative to earlier antidepressants such as the tricyclics and MAO inhibitors.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

The patient’s long-term use of a first-generation depot antipsychotic and the involuntary symptoms presented suggest a diagnosis of tardive dyskinesia. Acute anxiety is unlikely as the patient has a long standing relationship with their psychiatrist and the symptom combination does not fit. Akathisia, characterized by restlessness and leg movement, is also an unlikely diagnosis. Neuroleptic malignant syndrome (NMS) can be ruled out as the patient has had symptoms for two years. The patient is compliant with medication, has no psychotic symptoms, and is well-functioning in their job and home life, making a relapse of schizophrenia an incorrect diagnosis.

While NICE recommends mirtazapine for the treatment of PTSD, its license only permits its use for major depression.

Antidepressants (Licensed Indications)

The following table outlines the specific licensed indications for antidepressants in adults, as per the Maudsley Guidelines and the British National Formulary. It is important to note that all antidepressants are indicated for depression.

– Nocturnal enuresis in children: Amitriptyline, Imipramine, Nortriptyline
– Phobic and obsessional states: Clomipramine
– Adjunctive treatment of cataplexy associated with narcolepsy: Clomipramine
– Panic disorder and agoraphobia: Citalopram, Escitalopram, Sertraline, Paroxetine, Venlafaxine
– Social anxiety/phobia: Escitalopram, Paroxetine, Sertraline, Moclobemide, Venlafaxine
– Generalised anxiety disorder: Escitalopram, Paroxetine, Duloxetine, Venlafaxine
– OCD: Escitalopram, Fluoxetine, Fluvoxamine, Paroxetine, Sertraline, Clomipramine
– Bulimia nervosa: Fluoxetine
– PTSD: Paroxetine, Sertraline

Drug Stability

The stability of drugs can vary greatly, with some medications being unable to be included in compliance aids due to their susceptibility to environmental factors. Certain drugs have a tendency to absorb moisture from the air, rendering them ineffective, with light known to accelerate this process. Examples of drugs that are unsuitable for compliance aids due to their susceptibility to environmental factors include Sodium valproate, Zopiclone, Venlafaxine, Topiramate, Methylphenidate, Mirtazapine, Olanzapine, Amisulpride, and Aripiprazole.

Contrary to popular belief, the risk of neuroleptic malignant syndrome is not higher with depot antipsychotics compared to oral drugs. Additionally, there is no evidence to suggest that a prior history of NMS should prevent the use of depot antipsychotics. While caution may be warranted, a history of NMS is not a complete contraindication for depot antipsychotic use. These findings were reported by Patel in a 2005 article titled Why aren’t depot antipsychotics prescribed more often and what can be done about it? published in Advances in Psychiatric Treatment.

, coma, respiratory depression (rare)

According to a recent study by Ran (2019), lithium carbonate has been found to have a neuroprotective effect in individuals who have experienced a stroke. The study conducted exploratory analyses of neuroanatomical and cognitive outcomes in a poststroke population. It is interesting to note that while lithium is contraindicated in individuals with Addison’s disease, it is only cautioned in individuals with QT prolongation. Hypothyroidism (untreated) is also a contraindication for lithium. Addison’s disease is a condition characterized by inadequate production of cortisol and aldosterone by the adrenal cortex, leading to symptoms such as fatigue, gastrointestinal abnormalities, changes in skin pigmentation, and mood changes. In some cases, acute adrenal failure can occur, which is a serious condition that develops rapidly. The cause of Addison’s disease is often due to the body’s immune system mistakenly attacking the adrenal glands, causing progressive damage to the adrenal cortex.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Antipsychotics and Sudden Death: Thioridazine and QTc Prolongation

Antipsychotic medications are known to carry a risk of sudden death, particularly due to their effects on cardiac function. Thioridazine, in particular, has been found to have pronounced effects on potassium channels and significantly prolongs the QTc interval, which is a measure of the time it takes for the heart to repolarize after each beat. This prolongation can lead to a potentially fatal arrhythmia known as torsades de pointes. As a result, thioridazine is most strongly associated with sudden death among antipsychotics.

However, all antipsychotics carry some degree of risk for QTc prolongation and should be closely monitored for changes in this interval. This is especially important for patients with preexisting cardiac conditions of other risk factors for arrhythmias. Regular electrocardiogram (ECG) monitoring may be necessary to detect any changes in QTc interval and adjust medication accordingly. By carefully monitoring patients and taking appropriate precautions, healthcare providers can help minimize the risk of sudden death associated with antipsychotic use.

Hyponatremia in Psychiatric Patients

Hyponatremia, of low serum sodium, can occur in psychiatric patients due to the disorder itself, its treatment, of other medical conditions. Symptoms include nausea, confusion, seizures, and muscular cramps. Drug-induced hyponatremia is known as the syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH), which results from excessive secretion of ADH and fluid overload. Diagnosis is based on clinically euvolaemic state with low serum sodium and osmolality, raised urine sodium and osmolality. SSRIs, SNRIs, and tricyclics are the most common drugs that can cause SIADH. Risk factors for SIADH include starting a new drug, and treatment usually involves fluid restriction and sometimes demeclocycline.

Pregnant women who take valproate have a high risk of giving birth to children with congenital malformations, with rates ranging from 6-11%. The North American Antiepileptic Drug Registry found that 10.7% of children born to women taking valproate monotherapy had major malformations, while the UK Epilepsy and Pregnancy Register reported a rate of 6.2%. The most common malformations are heart and facial defects, as well as neural tube, urogenital, and skeletal defects. While folic acid supplementation may help reduce the risk of malformations, it is strongly recommended that women avoid taking valproate during pregnancy.

Debrisoquine hydroxylase is responsible for the metabolism of several antidepressants such as tricyclics, SSRIs, venlafaxine, and others. Poor metabolisers may experience more side effects from these medications, while ultra-rapid metabolisers may require higher doses.

The Cytochrome P450 system is a group of enzymes that metabolize drugs by altering their functional groups. The system is located in the liver and small intestine and is involved in drug interactions through enzyme induction of inhibition. Notable inducers include smoking, alcohol, and St John’s Wort, while notable inhibitors include grapefruit juice and some SSRIs. CYP2D6 is important due to genetic polymorphism, and CYP3A4 is the most abundant subfamily and is commonly involved in interactions. Grapefruit juice inhibits both CYP1A2 and CYP3A4, while tobacco smoking induces CYP1A2. The table summarizes the main substrates, inhibitors, and inducers for each CYP enzyme.

Serotonin Syndrome and Neuroleptic Malignant Syndrome are two conditions that can be difficult to differentiate. Serotonin Syndrome is caused by excess serotonergic activity in the CNS and is characterized by neuromuscular abnormalities, altered mental state, and autonomic dysfunction. On the other hand, Neuroleptic Malignant Syndrome is a rare acute disorder of thermoregulation and neuromotor control that is almost exclusively caused by antipsychotics. The symptoms of both syndromes can overlap, but there are some distinguishing clinical features. Hyper-reflexia, ocular clonus, and tremors are more prominent in Serotonin Syndrome, while Neuroleptic Malignant Syndrome is characterized by uniform ‘lead-pipe’ rigidity and hyporeflexia. Symptoms of Serotonin Syndrome usually resolve within a few days of stopping the medication, while Neuroleptic Malignant Syndrome can take up to 14 days to remit with appropriate treatment. The following table provides a useful guide to the main differentials of Serotonin Syndrome and Neuroleptic Malignant Syndrome.

In the treatment of Alzheimer’s disease, acetylcholinesterase inhibitors such as galantamine are utilized to enhance central acetylcholine levels. Although they share this common mechanism of action, there are variations in how they function. Unlike galantamine, rivastigmine has the ability to inhibit butyrylcholinesterase.

It is not advisable to limit fluid intake in cases of lithium-induced DI as it can result in severe hypernatremia.

Lithium – Pharmacology

Pharmacokinetics:
Lithium salts are rapidly absorbed following oral administration and are almost exclusively excreted by the kidneys unchanged. Blood samples for lithium should be taken 12 hours post-dose.

Ebstein’s:
Ebstein’s anomaly is a congenital malformation consisting of a prolapse of the tricuspid valve into the right ventricle. It occurs in 1:20,000 of the general population. Initial data suggested it was more common in those using lithium but this had not held to be true.

Contraindications:
Addison’s disease, Brugada syndrome, cardiac disease associated with rhythm disorders, clinically significant renal impairment, untreated of untreatable hypothyroidism, low sodium levels.

Side-effects:
Common side effects include nausea, tremor, polyuria/polydipsia, rash/dermatitis, blurred vision, dizziness, decreased appetite, drowsiness, metallic taste, and diarrhea. Side-effects are often dose-related.

Long-term use is associated with hypothyroidism, hyperthyroidism, hypercalcemia/hyperparathyroidism, irreversible nephrogenic diabetes insipidus, and reduced GFR.

Lithium-induced diabetes insipidus:
Treatment options include stopping lithium (if feasible), keeping levels within 0.4-0.8 mmol/L, once-daily dose of the drug taken at bedtime, amiloride, thiazide diuretics, indomethacin, and desmopressin.

Toxicity:
Lithium salts have a narrow therapeutic/toxic ratio. Risk factors for lithium toxicity include drugs altering renal function, decreased circulating volume, infections, fever, decreased oral intake of water, renal insufficiency, and nephrogenic diabetes insipidus. Features of lithium toxicity include GI symptoms and neuro symptoms.

Pre-prescribing:
Before prescribing lithium, renal function, cardiac function, thyroid function, FBC, and BMI should be checked. Women of childbearing age should be advised regarding contraception, and information about toxicity should be provided.

Monitoring:
Lithium blood levels should be checked weekly until stable, and then every 3-6 months once stable. Thyroid and renal function should be checked every 6 months. Patients should be issued with an information booklet, alert card, and record book.

Discontinuation symptoms are common when stopping most antidepressants, typically appearing within 5 days of treatment cessation. However, these symptoms are more likely to occur with short half-life drugs like paroxetine, especially when doses are missed. It’s important to note that discontinuing paroxetine may lead to suicidal thoughts, so patients should be informed of the potential risks associated with poor compliance.

Antidepressants can cause discontinuation symptoms when patients stop taking them, regardless of the type of antidepressant. These symptoms usually occur within 5 days of stopping the medication and can last up to 3 weeks. Symptoms include flu-like symptoms, dizziness, insomnia, vivid dreams, irritability, crying spells, and sensory symptoms. SSRIs and related drugs with short half-lives, such as paroxetine and venlafaxine, are particularly associated with discontinuation symptoms. Tapering antidepressants at the end of treatment is recommended to prevent these symptoms. TCAs and MAOIs are also associated with discontinuation symptoms, with amitriptyline and imipramine being the most common TCAs and all MAOIs being associated with prominent discontinuation symptoms. Patients at highest risk for discontinuation symptoms include those on antidepressants with shorter half-lives, those who have been taking antidepressants for 8 weeks of longer, those using higher doses, younger people, and those who have experienced discontinuation symptoms before. Agomelatine is not associated with any discontinuation syndrome. If a discontinuation reaction occurs, restarting the antidepressant of switching to an alternative with a longer half-life and tapering more slowly may be necessary. Explanation and reassurance are often sufficient for mild symptoms. These guidelines are based on the Maudsley Guidelines 14th Edition and a study by Tint (2008).

Antipsychotics can be classified in different ways, with the most common being typical (first generation) and atypical (second generation) types. Typical antipsychotics block dopamine (D2) receptors and have varying degrees of M1, Alpha-1, and H1 receptor blockade. Atypical antipsychotics have a lower propensity for extrapyramidal side-effects and are attributed to the combination of relatively lower D2 antagonism with 5HT2A antagonism. They are also classified by structure, with examples including phenothiazines, butyrophenones, thioxanthenes, diphenylbutylpiperidine, dibenzodiazepines, benzoxazoles, thienobenzodiazepine, substituted benzamides, and arylpiperidylindole (quinolone). Studies have found little evidence to support the superiority of atypicals over typicals in terms of efficacy, discontinuation rates, of adherence, with the main difference being the side-effect profile. The Royal College also favors classification by structure.

Antidepressants and Weight Gain

Studies suggest that certain types of antidepressants, such as tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs), may be more likely to cause weight gain than newer antidepressants like selective serotonin reuptake inhibitors (SSRIs). However, mirtazapine, a newer antidepressant, may have a similar risk for weight gain as TCAs. Among SSRIs, paroxetine may have a higher risk for weight gain during long-term treatment compared to other SSRIs. On the other hand, bupropion and nefazodone may have a lower risk for weight gain than SSRIs in the long term.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Hepatic Impairment: Recommended Drugs

Patients with hepatic impairment may experience reduced ability to metabolize drugs, toxicity, enhanced dose-related side effects, reduced ability to synthesize plasma proteins, and elevated levels of drugs subject to first-pass metabolism due to reduced hepatic blood flow. The Maudsley Guidelines 14th Ed recommends the following drugs for patients with hepatic impairment:

Antipsychotics: Paliperidone (if depot required), Amisulpride, Sulpiride

Antidepressants: Sertraline, Citalopram, Paroxetine, Vortioxetine (avoid TCA and MAOI)

Mood stabilizers: Lithium

Sedatives: Lorazepam, Oxazepam, Temazepam, Zopiclone 3.75mg (with care)

The onset of antipsychotic effect is noticeable within the first week of treatment, as reported by a large meta-analysis of almost 7,500 patients. This study found that there was a significant improvement of nearly 22% in the first two weeks of treatment, which contradicts the previous belief that it may take two to four weeks for antipsychotic action to take effect. The reduction in BPRS scores was as follows: 13.8% within the first week, 8.1% in the second week, 4.2% in the third week, and 4.7% in the fourth week.

Antidepressants (Licensed Indications)

The following table outlines the specific licensed indications for antidepressants in adults, as per the Maudsley Guidelines and the British National Formulary. It is important to note that all antidepressants are indicated for depression.

– Nocturnal enuresis in children: Amitriptyline, Imipramine, Nortriptyline
– Phobic and obsessional states: Clomipramine
– Adjunctive treatment of cataplexy associated with narcolepsy: Clomipramine
– Panic disorder and agoraphobia: Citalopram, Escitalopram, Sertraline, Paroxetine, Venlafaxine
– Social anxiety/phobia: Escitalopram, Paroxetine, Sertraline, Moclobemide, Venlafaxine
– Generalised anxiety disorder: Escitalopram, Paroxetine, Duloxetine, Venlafaxine
– OCD: Escitalopram, Fluoxetine, Fluvoxamine, Paroxetine, Sertraline, Clomipramine
– Bulimia nervosa: Fluoxetine
– PTSD: Paroxetine, Sertraline