Patients who have been bitten by a venomous snake, such as the adder in the UK, should be admitted to the hospital for a minimum of 24 hours. While most snake bites only cause localized symptoms, there is a small chance of life-threatening reactions to the venom. When patients arrive at the emergency department after a snake bite, they should undergo a quick assessment to determine the severity of the envenoming and receive resuscitation if necessary. If indicated, anti-venom should be administered. Following this, patients should be closely monitored for changes in blood pressure and the progression of envenoming for at least 24 hours.

Further Reading:

Snake bites in the UK are primarily caused by the adder, which is the only venomous snake species native to the country. While most adder bites result in minor symptoms such as pain, swelling, and inflammation, there have been cases of life-threatening illness and fatalities. Additionally, there are instances where venomous snakes that are kept legally or illegally also cause bites in the UK.

Adder bites typically occur from early spring to late autumn, with the hand being the most common site of the bite. Symptoms can be local or systemic, with local symptoms including sharp pain, tingling or numbness, and swelling that spreads proximally. Systemic symptoms may include spreading pain, tenderness, inflammation, regional lymph node enlargement, and bruising. In severe cases, anaphylaxis can occur, leading to symptoms such as nausea, vomiting, abdominal pain, diarrhea, and shock.

It is important for clinicians to be aware of the potential complications and complications associated with adder bites. These can include acute renal failure, pulmonary and cerebral edema, acute gastric dilatation, paralytic ileus, acute pancreatitis, and coma and seizures. Anaphylaxis symptoms can appear within minutes or be delayed for hours, and hypotension is a critical sign to monitor.

Initial investigations for adder bites include blood tests, ECG, and vital sign monitoring. Further investigations such as chest X-ray may be necessary based on clinical signs. Blood tests may reveal abnormalities such as leukocytosis, raised hematocrit, anemia, thrombocytopenia, and abnormal clotting profile. ECG changes may include tachyarrhythmias, bradyarrhythmias, atrial fibrillation, and ST segment changes.

First aid measures at the scene include immobilizing the patient and the bitten limb, avoiding aspirin and ibuprofen, and cleaning the wound site in the hospital. Tetanus prophylaxis should be considered. In cases of anaphylaxis, prompt administration of IM adrenaline is necessary. In the hospital, rapid assessment and appropriate resuscitation with intravenous fluids are required.

Antivenom may be indicated in cases of hypotension, systemic envenoming, ECG abnormalities, peripheral neutrophil leucocytosis, elevated serum creatine kinase or metabolic acidosis, and extensive or rapidly spreading local swelling. Zagreb antivenom is commonly used in the UK, with an initial dose of 8 mL

The recommended dose of adrenaline is 7 mg per kilogram of body weight, with a maximum limit of 500 mg.

Local anaesthetics, such as lidocaine, bupivacaine, and prilocaine, are commonly used in the emergency department for topical or local infiltration to establish a field block. Lidocaine is often the first choice for field block prior to central line insertion. These anaesthetics work by blocking sodium channels, preventing the propagation of action potentials.

However, local anaesthetics can enter the systemic circulation and cause toxic side effects if administered in high doses. Clinicians must be aware of the signs and symptoms of local anaesthetic systemic toxicity (LAST) and know how to respond. Early signs of LAST include numbness around the mouth or tongue, metallic taste, dizziness, visual and auditory disturbances, disorientation, and drowsiness. If not addressed, LAST can progress to more severe symptoms such as seizures, coma, respiratory depression, and cardiovascular dysfunction.

The management of LAST is largely supportive. Immediate steps include stopping the administration of local anaesthetic, calling for help, providing 100% oxygen and securing the airway, establishing IV access, and controlling seizures with benzodiazepines or other medications. Cardiovascular status should be continuously assessed, and conventional therapies may be used to treat hypotension or arrhythmias. Intravenous lipid emulsion (intralipid) may also be considered as a treatment option.

If the patient goes into cardiac arrest, CPR should be initiated following ALS arrest algorithms, but lidocaine should not be used as an anti-arrhythmic therapy. Prolonged resuscitation may be necessary, and intravenous lipid emulsion should be administered. After the acute episode, the patient should be transferred to a clinical area with appropriate equipment and staff for further monitoring and care.

It is important to report cases of local anaesthetic toxicity to the appropriate authorities, such as the National Patient Safety Agency in the UK or the Irish Medicines Board in the Republic of Ireland. Additionally, regular clinical review should be conducted to exclude pancreatitis, as intravenous lipid emulsion can interfere with amylase or lipase assays.

Organophosphate poisoning is characterized by a set of symptoms known as SLUDGE (Salivation, Lacrimation, Urination, Defecation, Gastric cramps, Emesis). Additionally, individuals affected may experience pinpoint pupils, profuse sweating, tremors, and confusion. Organophosphates serve as the foundation for various weaponized nerve agents like Sarin and VX, which were infamously employed by the terrorist group Aum Shinrikyo during multiple attacks in Tokyo in the mid-1990s. While SLUDGE is a commonly used acronym to recall the clinical features, it is important to note that other symptoms such as pinpoint pupils, profuse sweating, tremors, and confusion are not included in the acronym.

Further Reading:

Chemical incidents can occur as a result of leaks, spills, explosions, fires, terrorism, or the use of chemicals during wars. Industrial sites that use chemicals are required to conduct risk assessments and have accident plans in place for such incidents. Health services are responsible for decontamination, unless mass casualties are involved, and all acute health trusts must have major incident plans in place.

When responding to a chemical incident, hospitals prioritize containment of the incident and prevention of secondary contamination, triage with basic first aid, decontamination if not done at the scene, recognition and management of toxidromes (symptoms caused by exposure to specific toxins), appropriate supportive or antidotal treatment, transfer to definitive treatment, a safe end to the hospital response, and continuation of business after the event.

To obtain advice when dealing with chemical incidents, the two main bodies are Toxbase and the National Poisons Information Service. Signage on containers carrying chemicals and material safety data sheets (MSDS) accompanying chemicals also provide information on the chemical contents and their hazards.

Contamination in chemical incidents can occur in three phases: primary contamination from the initial incident, secondary contamination spread via contaminated people leaving the initial scene, and tertiary contamination spread to the environment, including becoming airborne and waterborne. The ideal personal protective equipment (PPE) for chemical incidents is an all-in-one chemical-resistant overall with integral head/visor and hands/feet worn with a mask, gloves, and boots.

Decontamination of contaminated individuals involves the removal and disposal of contaminated clothing, followed by either dry or wet decontamination. Dry decontamination is suitable for patients contaminated with non-caustic chemicals and involves blotting and rubbing exposed skin gently with dry absorbent material. Wet decontamination is suitable for patients contaminated with caustic chemicals and involves a warm water shower while cleaning the body with simple detergent.

After decontamination, the focus shifts to assessing the extent of any possible poisoning and managing it. The patient’s history should establish the chemical the patient was exposed to, the volume and concentration of the chemical, the route of exposure, any protective measures in place, and any treatment given. Most chemical poisonings require supportive care using standard resuscitation principles, while some chemicals have specific antidotes. Identifying toxidromes can be useful in guiding treatment, and specific antidotes may be administered accordingly.

The cardiotoxic effects of TCAs occur when they block sodium channels, leading to broadening of the QRS complex, and potassium channels, resulting in prolongation of the QT interval. The severity of adverse events is directly related to the degree of QRS broadening. If the QRS complex is greater than 100 ms, it is likely that seizures may occur. If the QRS complex exceeds 160 ms, ventricular arrhythmias may be predicted. In cases of TCA overdose, certain changes can be observed on an ECG. These include sinus tachycardia, which is very common, prolongation of the PR interval, broadening of the QRS complex, prolongation of the QT interval, and in severe cases, ventricular arrhythmias.

Hypomagnesaemia frequently occurs alongside hypokalaemia. It is important to note that potassium levels may not improve with supplementation until the magnesium deficiency is addressed.

Further Reading:

Vasoactive drugs can be classified into three categories: inotropes, vasopressors, and unclassified. Inotropes are drugs that alter the force of muscular contraction, particularly in the heart. They primarily stimulate adrenergic receptors and increase myocardial contractility. Commonly used inotropes include adrenaline, dobutamine, dopamine, isoprenaline, and ephedrine.

Vasopressors, on the other hand, increase systemic vascular resistance (SVR) by stimulating alpha-1 receptors, causing vasoconstriction. This leads to an increase in blood pressure. Commonly used vasopressors include norepinephrine, metaraminol, phenylephrine, and vasopressin.

Electrolytes, such as potassium, are essential for proper bodily function. Solutions containing potassium are often given to patients to prevent or treat hypokalemia (low potassium levels). However, administering too much potassium can lead to hyperkalemia (high potassium levels), which can cause dangerous arrhythmias. It is important to monitor potassium levels and administer it at a controlled rate to avoid complications.

Hyperkalemia can be caused by various factors, including excessive potassium intake, decreased renal excretion, endocrine disorders, certain medications, metabolic acidosis, tissue destruction, and massive blood transfusion. It can present with cardiovascular, respiratory, gastrointestinal, and neuromuscular symptoms. ECG changes, such as tall tented T-waves, prolonged PR interval, flat P-waves, widened QRS complex, and sine wave, are also characteristic of hyperkalemia.

In summary, vasoactive drugs can be categorized as inotropes, vasopressors, or unclassified. Inotropes increase myocardial contractility, while vasopressors increase systemic vascular resistance. Electrolytes, particularly potassium, are important for bodily function, but administering too much can lead to hyperkalemia. Monitoring potassium levels and ECG changes is crucial in managing hyperkalemia.

To ensure prompt response in case of an adverse reaction, it is important to have adrenaline, antihistamine, and steroid readily available when administering Zagreb antivenom.

Further Reading:

Snake bites in the UK are primarily caused by the adder, which is the only venomous snake species native to the country. While most adder bites result in minor symptoms such as pain, swelling, and inflammation, there have been cases of life-threatening illness and fatalities. Additionally, there are instances where venomous snakes that are kept legally or illegally also cause bites in the UK.

Adder bites typically occur from early spring to late autumn, with the hand being the most common site of the bite. Symptoms can be local or systemic, with local symptoms including sharp pain, tingling or numbness, and swelling that spreads proximally. Systemic symptoms may include spreading pain, tenderness, inflammation, regional lymph node enlargement, and bruising. In severe cases, anaphylaxis can occur, leading to symptoms such as nausea, vomiting, abdominal pain, diarrhea, and shock.

It is important for clinicians to be aware of the potential complications and complications associated with adder bites. These can include acute renal failure, pulmonary and cerebral edema, acute gastric dilatation, paralytic ileus, acute pancreatitis, and coma and seizures. Anaphylaxis symptoms can appear within minutes or be delayed for hours, and hypotension is a critical sign to monitor.

Initial investigations for adder bites include blood tests, ECG, and vital sign monitoring. Further investigations such as chest X-ray may be necessary based on clinical signs. Blood tests may reveal abnormalities such as leukocytosis, raised hematocrit, anemia, thrombocytopenia, and abnormal clotting profile. ECG changes may include tachyarrhythmias, bradyarrhythmias, atrial fibrillation, and ST segment changes.

First aid measures at the scene include immobilizing the patient and the bitten limb, avoiding aspirin and ibuprofen, and cleaning the wound site in the hospital. Tetanus prophylaxis should be considered. In cases of anaphylaxis, prompt administration of IM adrenaline is necessary. In the hospital, rapid assessment and appropriate resuscitation with intravenous fluids are required.

Antivenom may be indicated in cases of hypotension, systemic envenoming, ECG abnormalities, peripheral neutrophil leucocytosis, elevated serum creatine kinase or metabolic acidosis, and extensive or rapidly spreading local swelling. Zagreb antivenom is commonly used in the UK, with an initial dose of 8 mL.

The drugs that have the highest association with the development of drug-induced lupus are procainamide and hydralazine. While some of the other medications mentioned in this question have also been reported to cause drug-induced lupus, the strength of their association is much weaker.

Theophylline is a medication used to treat severe asthma. It is a bronchodilator that comes in modified-release forms, which can maintain therapeutic levels in the blood for 12 hours. Theophylline works by inhibiting phosphodiesterase and blocking the breakdown of cyclic AMP. It also competes with adenosine on A1 and A2 receptors.

Achieving the right dose of theophylline can be challenging because there is a narrow range between therapeutic and toxic levels. The half-life of theophylline can be influenced by various factors, further complicating dosage adjustments. It is recommended to aim for serum levels of 10-20 mg/l six to eight hours after the last dose.

Unlike many other medications, the specific brand of theophylline can significantly impact its effects. Therefore, it is important to prescribe theophylline by both its brand name and generic name.

Several factors can increase the half-life of theophylline, including heart failure, cirrhosis, viral infections, and certain drugs. Conversely, smoking, heavy drinking, and certain medications can decrease the half-life of theophylline.

There are several drugs that can either increase or decrease the plasma concentration of theophylline. Calcium channel blockers, cimetidine, fluconazole, macrolides, methotrexate, and quinolones can increase the concentration. On the other hand, carbamazepine, phenobarbitol, phenytoin, rifampicin, and St. John’s wort can decrease the concentration.

The clinical symptoms of theophylline toxicity are more closely associated with acute overdose rather than chronic overexposure. Common symptoms include headache, dizziness, nausea, vomiting, abdominal pain, rapid heartbeat, dysrhythmias, seizures, mild metabolic acidosis, low potassium, low magnesium, low phosphates, abnormal calcium levels, and high blood sugar.

Seizures are more prevalent in acute overdose cases, while chronic overdose typically presents with minimal gastrointestinal symptoms. Cardiac dysrhythmias are more common in chronic overdose situations compared to acute overdose.

The use of antibiotics can impact the effectiveness of warfarin and other coumarin anticoagulants. This can lead to changes in the International Normalized Ratio (INR) and, in severe cases, increase the risk of bleeding. Some antibiotics, such as chloramphenicol, ciprofloxacin, co-trimoxazole, doxycycline, erythromycin, macrolides (e.g., clarithromycin), metronidazole, ofloxacin, and sulphonamide, are known to enhance the anticoagulant effect of warfarin. However, cefalexin is considered relatively safe and is the most suitable option in this situation.

Fluoroquinolones are a rare but acknowledged cause of tendinopathy and spontaneous tendon rupture. It is estimated that tendon disorders related to fluoroquinolones occur in approximately 15 to 20 out of every 100,000 patients. These issues are most commonly observed in individuals who are over the age of 60.

The Achilles tendon is the most frequently affected, although cases involving other tendons such as the quadriceps, peroneus brevis, extensor pollicis longus, the long head of biceps brachii, and rotator cuff tendons have also been reported. The exact underlying mechanism is not fully understood, but it is believed that fluoroquinolone drugs may hinder collagen function and/or disrupt blood supply to the tendon.

There are other risk factors associated with spontaneous tendon rupture, including corticosteroid therapy, hypercholesterolemia, gout, rheumatoid arthritis, long-term dialysis, and renal transplantation.

The Arthus reaction is a response that occurs when antigen/antibody complexes are formed in the skin after an antigen is injected. Although rare, these reactions can happen after receiving vaccines that contain tetanus toxoid or diphtheria toxoid. They are classified as a type III hypersensitivity reaction.

Arthus reactions are characterized by pain, swelling, induration, hemorrhage, and sometimes necrosis. Typically, these symptoms appear 4-12 hours after vaccination.

Type III hypersensitivity reactions occur when insoluble antigen-antibody complexes accumulate in different tissues and are not effectively cleared by the body’s innate immune cells. This leads to an inflammatory response in the affected tissues.

Some other examples of type III hypersensitivity reactions include immune complex glomerulonephritis, rheumatoid arthritis, systemic lupus erythematosus, serum sickness, and extrinsic allergic alveolitis.

Activated charcoal is a commonly used substance for decontamination in cases of poisoning. Its main function is to adsorb the molecules of the ingested toxin onto its surface.

Activated charcoal is a chemically inert form of carbon. It is a fine black powder that has no odor or taste. It is produced by subjecting carbonaceous matter to high temperatures, a process known as pyrolysis, and then concentrating it with a zinc chloride solution. This creates a network of pores within the charcoal, giving it a large absorptive area of approximately 3,000 m2/g. This porous structure helps prevent the absorption of the harmful toxin by up to 50%.

The usual dosage of activated charcoal is 50 grams for adults and 1 gram per kilogram of body weight for children. It can be administered orally or through a nasogastric tube. It is important to give the charcoal within one hour of ingestion, and it may be repeated after one hour if necessary.

However, there are certain situations where activated charcoal should not be used. If the patient is unconscious or in a coma, there is a risk of aspiration, so the charcoal should not be given. Similarly, if seizures are likely to occur, there is a risk of aspiration and the charcoal should be avoided. Additionally, if there is reduced gastrointestinal motility, there is a risk of obstruction, so activated charcoal should not be used in such cases.

Activated charcoal is effective in treating overdose with various drugs and toxins, including aspirin, paracetamol, barbiturates, tricyclic antidepressants, digoxin, amphetamines, morphine, cocaine, and phenothiazines. However, it is ineffective in treating overdose with substances such as iron, lithium, boric acid, cyanide, ethanol, ethylene glycol, methanol, malathion, DDT, carbamate, hydrocarbon, strong acids, or alkalis.

There are some potential adverse effects associated with activated charcoal. These include nausea and vomiting, diarrhea, constipation, bezoar formation (a mass of undigested material that can cause blockages), bowel obstruction, pulmonary aspiration (inhaling the charcoal into the lungs), and impaired absorption of oral medications or antidotes.

The use of NSAIDs in the third trimester of pregnancy is linked to several risks. These risks include delayed onset of labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus, which is a condition where bilirubin causes brain dysfunction. Additionally, there is a slight increase in the risk of first-trimester abortion if NSAIDs are used early in pregnancy.

Below is a list outlining commonly encountered drugs that have adverse effects during pregnancy:

ACE inhibitors (e.g. ramipril): If given in the second and third trimester, these drugs can cause hypoperfusion, renal failure, and the oligohydramnios sequence.

Aminoglycosides (e.g. gentamicin): These drugs can cause ototoxicity and deafness.

Aspirin: High doses of aspirin can lead to first-trimester abortions, delayed onset of labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses (e.g. 75 mg) do not pose a significant risk.

Benzodiazepines (e.g. diazepam): When given late in pregnancy, these drugs can cause respiratory depression and a neonatal withdrawal syndrome.

Calcium-channel blockers: If given in the first trimester, these drugs can cause phalangeal abnormalities. If given in the second and third trimester, they can lead to fetal growth retardation.

Carbamazepine: This drug can cause hemorrhagic disease of the newborn and neural tube defects.

Chloramphenicol: Use of this drug can result in grey baby syndrome.

Corticosteroids: If given in the first trimester, corticosteroids may cause orofacial clefts.

Danazol: If given in the first trimester, this drug can cause masculinization of the female fetuses genitals.

Finasteride: Pregnant women should avoid handling finasteride. Crushed or broken tablets can be absorbed through the skin and affect male sex organ development.

Haloperidol: If given in the first trimester, this drug may cause limb malformations. If given in the third trimester, there is an increased risk of extrapyramidal symptoms in the neonate.

Heparin: Use of heparin during pregnancy can lead to maternal bleeding and thrombocytopenia.

Isoniazid: This drug can cause maternal liver damage

The following list provides a summary of common causes for different acid-base disorders.

Respiratory alkalosis can be caused by hyperventilation, such as during periods of anxiety. It can also be a result of conditions like pulmonary embolism, CNS disorders (such as stroke or encephalitis), altitude, pregnancy, or the early stages of aspirin overdose.

Respiratory acidosis is often associated with chronic obstructive pulmonary disease (COPD) or life-threatening asthma. It can also occur due to pulmonary edema, sedative drug overdose (such as opiates or benzodiazepines), neuromuscular disease, obesity, or other respiratory conditions.

Metabolic alkalosis can be caused by vomiting, potassium depletion (often due to diuretic usage), Cushing’s syndrome, or Conn’s syndrome.

Metabolic acidosis with a raised anion gap can occur due to lactic acidosis (such as in cases of hypoxemia, shock, sepsis, or infarction) or ketoacidosis (such as in diabetes, starvation, or alcohol excess). It can also be a result of renal failure or poisoning (such as in late stages of aspirin overdose, methanol or ethylene glycol ingestion).

Metabolic acidosis with a normal anion gap can be caused by conditions like renal tubular acidosis, diarrhea, ammonium chloride ingestion, or adrenal insufficiency.

Loop diuretics, like furosemide, commonly result in several electrolyte imbalances. These imbalances include hyponatremia, which is a decrease in sodium levels in the blood. Another common imbalance is hypokalemia, which refers to low levels of potassium. Additionally, loop diuretics can cause hypocalcemia, a condition characterized by low levels of calcium in the blood. Another electrolyte affected by loop diuretics is magnesium, as they can lead to hypomagnesemia, which is a deficiency of magnesium. Lastly, loop diuretics can cause hypochloremic alkalosis, which is a condition characterized by low levels of chloride in the blood and an increase in blood pH.

Digoxin is a medication used to treat atrial fibrillation and flutter as well as congestive cardiac failure. It belongs to a class of drugs called cardiac glycosides. Digoxin works by inhibiting the Na/K ATPase pump in the cardiac myocytes, which are the cells of the heart. This inhibition leads to an increase in the concentration of sodium inside the cells and indirectly increases the availability of calcium through the Na/Ca exchange mechanism. The rise in intracellular calcium levels results in a positive inotropic effect, meaning it strengthens the force of the heart’s contractions, and a negative chronotropic effect, meaning it slows down the heart rate.

However, it’s important to note that digoxin can cause toxicity, which is characterized by high levels of potassium in the blood, known as hyperkalemia. Normally, the Na/K ATPase pump helps maintain the balance of sodium and potassium by allowing sodium to leave the cells and potassium to enter. When digoxin blocks this pump, it disrupts this balance and leads to higher levels of potassium in the bloodstream.

Interestingly, the risk of developing digoxin toxicity is higher in individuals with low levels of potassium, known as hypokalemia. This is because digoxin binds to the ATPase pump at the same site as potassium. When potassium levels are low, digoxin can more easily bind to the ATPase pump and exert its inhibitory effects.

In summary, digoxin is a cardiac glycoside that is used to treat certain heart conditions. It works by inhibiting the Na/K ATPase pump, leading to increased intracellular calcium levels and resulting in a positive inotropic effect and negative chronotropic effect. However, digoxin can also cause toxicity, leading to high levels of potassium in the blood. The risk of toxicity is higher in individuals with low potassium levels.

Gynaecomastia, a condition characterized by the enlargement of breast tissue in males, can be caused by certain drugs. Some medications that have been associated with gynaecomastia include Cimetidine, Omeprazole, Spironolactone, Digoxin, Furosemide, Finasteride, and certain antipsychotics. Interestingly, Ranitidine, another medication commonly used for gastric issues, does not tend to cause gynaecomastia. In fact, studies have shown that gynaecomastia caused by Cimetidine can be resolved when it is substituted with Ranitidine.

Tricyclic antidepressant (TCA) overdose is a significant problem in cases of drug overdose and is one of the most common causes of fatal drug poisoning. Any overdose of amitriptyline that exceeds 10 mg/kg has the potential to be life-threatening. If the overdose surpasses 30 mg/kg, it will lead to severe toxicity, cardiotoxicity, and coma.

The toxic effects of TCAs are caused by various pharmacological actions. These include anticholinergic effects, direct blocking of alpha-adrenergic receptors, inhibition of noradrenaline reuptake at the preganglionic synapse, blockade of sodium channels, and blockade of potassium channels.

Amiodarone is a medication that can have numerous harmful side effects, making it crucial to conduct a comprehensive clinical assessment before starting treatment with it. Some of the side effects associated with amiodarone include corneal microdeposits, photosensitivity, nausea, sleep disturbance, hyperthyroidism, hypothyroidism, acute hepatitis and jaundice, peripheral neuropathy, lung fibrosis, QT prolongation, and optic neuritis (although this is very rare). If optic neuritis occurs, immediate discontinuation of amiodarone is necessary to prevent the risk of blindness.

The majority of patients taking amiodarone experience corneal microdeposits, but these typically resolve after treatment is stopped and rarely affect vision. Amiodarone has a chemical structure similar to thyroxine and can bind to the nuclear thyroid receptor, leading to both hypothyroidism and hyperthyroidism. However, hypothyroidism is more commonly observed, affecting around 5-10% of patients.

Patients who have taken an overdose of tricyclic antidepressants (TCAs) should not be given phenytoin.

Further Reading:

Tricyclic antidepressant (TCA) overdose is a common occurrence in emergency departments, with drugs like amitriptyline and dosulepin being particularly dangerous. TCAs work by inhibiting the reuptake of norepinephrine and serotonin in the central nervous system. In cases of toxicity, TCAs block various receptors, including alpha-adrenergic, histaminic, muscarinic, and serotonin receptors. This can lead to symptoms such as hypotension, altered mental state, signs of anticholinergic toxicity, and serotonin receptor effects.

TCAs primarily cause cardiac toxicity by blocking sodium and potassium channels. This can result in a slowing of the action potential, prolongation of the QRS complex, and bradycardia. However, the blockade of muscarinic receptors also leads to tachycardia in TCA overdose. QT prolongation and Torsades de Pointes can occur due to potassium channel blockade. TCAs can also have a toxic effect on the myocardium, causing decreased cardiac contractility and hypotension.

Early symptoms of TCA overdose are related to their anticholinergic properties and may include dry mouth, pyrexia, dilated pupils, agitation, sinus tachycardia, blurred vision, flushed skin, tremor, and confusion. Severe poisoning can lead to arrhythmias, seizures, metabolic acidosis, and coma. ECG changes commonly seen in TCA overdose include sinus tachycardia, widening of the QRS complex, prolongation of the QT interval, and an R/S ratio >0.7 in lead aVR.

Management of TCA overdose involves ensuring a patent airway, administering activated charcoal if ingestion occurred within 1 hour and the airway is intact, and considering gastric lavage for life-threatening cases within 1 hour of ingestion. Serial ECGs and blood gas analysis are important for monitoring. Intravenous fluids and correction of hypoxia are the first-line therapies. IV sodium bicarbonate is used to treat haemodynamic instability caused by TCA overdose, and benzodiazepines are the treatment of choice for seizure control. Other treatments that may be considered include glucagon, magnesium sulfate, and intravenous lipid emulsion.

There are certain things to avoid in TCA overdose, such as anti-arrhythmics like quinidine and flecainide, as they can prolonged depolarization.

The earliest and most common clinical indication of malignant hyperthermia is typically an increase in end tidal CO2 levels.

Further Reading:

Malignant hyperthermia is a rare and life-threatening syndrome that can be triggered by certain medications in individuals who are genetically susceptible. The most common triggers are suxamethonium and inhalational anaesthetic agents. The syndrome is caused by the release of stored calcium ions from skeletal muscle cells, leading to uncontrolled muscle contraction and excessive heat production. This results in symptoms such as high fever, sweating, flushed skin, rapid heartbeat, and muscle rigidity. It can also lead to complications such as acute kidney injury, rhabdomyolysis, and metabolic acidosis. Treatment involves discontinuing the trigger medication, administering dantrolene to inhibit calcium release and promote muscle relaxation, and managing any associated complications such as hyperkalemia and acidosis. Referral to a malignant hyperthermia center for further investigation is also recommended.

Extrapyramidal side effects are most commonly seen with the piperazine phenothiazines (fluphenazine, prochlorperazine, and trifluoperazine) and butyrophenones (benperidol and haloperidol). Among these, haloperidol is the most frequently implicated antipsychotic drug.

Tardive dyskinesia, which involves involuntary rhythmic movements of the tongue, face, and jaw, typically occurs after prolonged treatment or high doses. It is the most severe manifestation of extrapyramidal symptoms, as it may become irreversible even after discontinuing the causative medication, and treatment options are generally ineffective.

Dystonia, characterized by abnormal movements of the face and body, is more commonly observed in children and young adults and tends to appear after only a few doses. Acute dystonia can be managed with intravenous administration of procyclidine (5 mg) or benzatropine (2 mg) as a bolus.

Akathisia refers to an unpleasant sensation of restlessness, while akinesia refers to an inability to initiate movement.

In individuals with renal impairment, there is an increased sensitivity of the brain to antipsychotic drugs, necessitating the use of reduced doses.

Elderly patients with dementia-related psychosis who are treated with haloperidol face an elevated risk of mortality. This is believed to be due to an increased likelihood of cardiovascular events and infections such as pneumonia.

Contraindications for the use of antipsychotic drugs include reduced consciousness or coma, central nervous system depression, and the presence of phaeochromocytoma.

During the third trimester of pregnancy, the use of selective serotonin reuptake inhibitors (SSRIs) has been associated with a discontinuation syndrome and persistent pulmonary hypertension of the newborn. It is important to be aware of the adverse effects of various drugs during pregnancy. For example, ACE inhibitors like ramipril, if given in the second and third trimester, can cause hypoperfusion, renal failure, and the oligohydramnios sequence. Aminoglycosides such as gentamicin can lead to ototoxicity and deafness. High doses of aspirin can result in first-trimester abortions, delayed onset labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses (e.g., 75 mg) do not pose significant risks. Late administration of benzodiazepines like diazepam during pregnancy can cause respiratory depression and a neonatal withdrawal syndrome. Calcium-channel blockers, if given in the first trimester, may cause phalangeal abnormalities, while their use in the second and third trimester can lead to fetal growth retardation. Carbamazepine has been associated with hemorrhagic disease of the newborn and neural tube defects. Chloramphenicol can cause grey baby syndrome. Corticosteroids, if given in the first trimester, may cause orofacial clefts. Danazol, if administered in the first trimester, can result in masculinization of the female fetuses genitals. Pregnant women should avoid handling crushed or broken tablets of finasteride as it can be absorbed through the skin and affect male sex organ development. Haloperidol, if given in the first trimester, may cause limb malformations, while its use in the third trimester increases the risk of extrapyramidal symptoms in the neonate. Heparin can lead to maternal bleeding and thrombocytopenia. Isoniazid can cause maternal liver damage and neuropathy and seizures in the neonate. Isotretinoin carries a high risk of teratogenicity, including multiple congenital malformations, spontaneous abortion, and intellectual disability. The use of lithium in the first trimester increases the risk of fetal cardiac malformations, while its use in the second and third trimesters can result in hypotonia, lethargy, feeding problems, hypothyroidism, goiter, and nephrogenic diabetes insipidus.

The differences in anti-inflammatory activity among NSAIDs are minimal, but there is significant variation in how individuals respond to and tolerate these drugs. Approximately 60% of patients will experience a positive response to any NSAID, and those who do not respond to one may find relief with another. Pain relief typically begins shortly after taking the first dose, and a full analgesic effect is usually achieved within a week. However, it may take up to 3 weeks to see an anti-inflammatory effect, which may not be easily assessed. If desired results are not achieved within these timeframes, it is recommended to try a different NSAID.

NSAIDs work by reducing the production of prostaglandins through the inhibition of the enzyme cyclo-oxygenase. Different NSAIDs vary in their selectivity for inhibiting different types of cyclo-oxygenase. Selective inhibition of cyclo-oxygenase-2 is associated with a lower risk of gastrointestinal intolerance. Other factors also play a role in susceptibility to gastrointestinal effects, so the choice of NSAID should consider the incidence of gastrointestinal and other side effects.

Ibuprofen, a propionic acid derivative, possesses anti-inflammatory, analgesic, and antipyretic properties. It generally has fewer side effects compared to other non-selective NSAIDs, but its anti-inflammatory properties are weaker. For rheumatoid arthritis, doses of 1.6 to 2.4 g daily are required, and it may not be suitable for conditions where inflammation is prominent, such as acute gout.

Naproxen is often a preferred choice due to its combination of good efficacy and low incidence of side effects. However, it does have a higher occurrence of side effects compared to ibuprofen.

Ketoprofen and diclofenac have similar anti-inflammatory properties to ibuprofen but are associated with more side effects.

Indometacin has an action that is equal to or superior to naproxen, but it also has a high incidence of side effects, including headache, dizziness, and gastrointestinal disturbances.

There is a significant link between methotrexate and the development of pulmonary fibrosis. While there have been instances of pulmonary fibrosis occurring as a result of infliximab, this particular side effect is more commonly associated with methotrexate use.

Methotrexate can also cause other side effects such as nausea and vomiting, abdominal pain, gastrointestinal bleeding, dizziness, stomatitis, hepatotoxicity, neutropenia, and pneumonitis.

The primary treatment for malignant hyperthermia is dantrolene. Dantrolene works by blocking the release of calcium through calcium channels, resulting in the relaxation of skeletal muscles.

Further Reading:

Malignant hyperthermia is a rare and life-threatening syndrome that can be triggered by certain medications in individuals who are genetically susceptible. The most common triggers are suxamethonium and inhalational anaesthetic agents. The syndrome is caused by the release of stored calcium ions from skeletal muscle cells, leading to uncontrolled muscle contraction and excessive heat production. This results in symptoms such as high fever, sweating, flushed skin, rapid heartbeat, and muscle rigidity. It can also lead to complications such as acute kidney injury, rhabdomyolysis, and metabolic acidosis. Treatment involves discontinuing the trigger medication, administering dantrolene to inhibit calcium release and promote muscle relaxation, and managing any associated complications such as hyperkalemia and acidosis. Referral to a malignant hyperthermia center for further investigation is also recommended.

Lithium toxicity presents with various symptoms, including nausea and vomiting, diarrhea, tremor, ataxia, confusion, increased muscle tone, clonus, nephrogenic diabetes insipidus, convulsions, coma, and renal failure. One notable symptom associated with digoxin toxicity is xanthopsia.

Activated charcoal is a commonly utilized substance for decontamination in cases of poisoning. Its main function is to attract and bind molecules of the ingested toxin onto its surface.

Activated charcoal is a chemically inert form of carbon. It is a fine black powder that has no odor or taste. This powder is created by subjecting carbonaceous matter to high heat, a process known as pyrolysis, and then concentrating it with a solution of zinc chloride. Through this process, the activated charcoal develops a complex network of pores, providing it with a large surface area of approximately 3,000 m2/g. This extensive surface area allows it to effectively hinder the absorption of the harmful toxin by up to 50%.

The typical dosage for adults is 50 grams, while children are usually given 1 gram per kilogram of body weight. Activated charcoal can be administered orally or through a nasogastric tube. It is crucial to administer it within one hour of ingestion, and if necessary, a second dose may be repeated after one hour.

Spironolactone is a medication used to treat conditions such as congestive cardiac failure, hypertension, hepatic cirrhosis with ascites and edema, and Conn’s syndrome. It functions as a competitive aldosterone receptor antagonist, primarily working in the distal convoluted tubule. In this area, it hinders the reabsorption of sodium ions and enhances the reabsorption of potassium ions. Spironolactone is commonly known as a potassium-sparing diuretic.

The main side effect of spironolactone is hyperkalemia, particularly when renal impairment is present. In severe cases, hyperkalemia can be life-threatening. Additionally, there is a notable occurrence of gastrointestinal disturbances, with nausea and vomiting being the most common. Women may experience menstrual disturbances, while men may develop gynecomastia, both of which are attributed to the antiandrogenic effects of spironolactone.

In managing patients with carbon monoxide poisoning, the primary intervention is providing 100% oxygen. This is because carbon monoxide has a higher affinity for hemoglobin than oxygen, leading to decreased oxygen delivery to tissues. By administering 100% oxygen, the patient is able to displace carbon monoxide from hemoglobin and increase oxygen levels in the blood, which is crucial for the patient’s recovery.

Further Reading:

Carbon monoxide (CO) is a dangerous gas that is produced by the combustion of hydrocarbon fuels and can be found in certain chemicals. It is colorless and odorless, making it difficult to detect. In England and Wales, there are approximately 60 deaths each year due to accidental CO poisoning.

When inhaled, carbon monoxide binds to haemoglobin in the blood, forming carboxyhaemoglobin (COHb). It has a higher affinity for haemoglobin than oxygen, causing a left-shift in the oxygen dissociation curve and resulting in tissue hypoxia. This means that even though there may be a normal level of oxygen in the blood, it is less readily released to the tissues.

The clinical features of carbon monoxide toxicity can vary depending on the severity of the poisoning. Mild or chronic poisoning may present with symptoms such as headache, nausea, vomiting, vertigo, confusion, and weakness. More severe poisoning can lead to intoxication, personality changes, breathlessness, pink skin and mucosae, hyperpyrexia, arrhythmias, seizures, blurred vision or blindness, deafness, extrapyramidal features, coma, or even death.

To help diagnose domestic carbon monoxide poisoning, there are four key questions that can be asked using the COMA acronym. These questions include asking about co-habitees and co-occupants in the house, whether symptoms improve outside of the house, the maintenance of boilers and cooking appliances, and the presence of a functioning CO alarm.

Typical carboxyhaemoglobin levels can vary depending on whether the individual is a smoker or non-smoker. Non-smokers typically have levels below 3%, while smokers may have levels below 10%. Symptomatic individuals usually have levels between 10-30%, and severe toxicity is indicated by levels above 30%.

When managing carbon monoxide poisoning, the first step is to administer 100% oxygen. Hyperbaric oxygen therapy may be considered for individuals with a COHb concentration of over 20% and additional risk factors such as loss of consciousness, neurological signs, myocardial ischemia or arrhythmia, or pregnancy. Other management strategies may include fluid resuscitation, sodium bicarbonate for metabolic acidosis, and mannitol for cerebral edema.