Tacrolimus is a calcineurin inhibitor used as an immunosuppressive agent used for prophylaxis of organ rejection post-transplant.

Pharmacology: Calcineurin inhibition leads to reduced T-lymphocyte signal transduction and IL-2 expression. It has a half-life of 12 hours (average).

Other off-label indications for the use of tacrolimus include Crohn disease, graft-versus-host disease (GVHD), myasthenia gravis, rheumatoid arthritis.

Adverse effects of tacrolimus includes:
Cardiovascular: Angina pectoris, cardiac arrhythmias, hypertension
Central nervous system: Abnormal dreams, headaches, insomnia, tremors.
Dermatologic: Acne vulgaris, alopecia, pruritis, rash
Endocrine and metabolic: Decreased serum bicarbonate, decreased serum iron, new-onset diabetes mellitus after transplant (NODAT), electrolyte disturbances.
Gastrointestinal: Abdominal pain, nausea, vomiting, diarrhoea
Genitourinary: Urinary tract infection
Hepatic: Abnormal hepatic function tests
Neuromuscular and skeletal: Arthralgia, muscle cramps
Ophthalmic: Blurred vision, visual disturbance
Otic: Otalgia, otitis media, tinnitus
Renal: Acute renal failure

Other options:
Sirolimus (a macrolide) is an mTOR inhibitor that blocks the response to IL-2 and has a half-life of 12–15 hours.
Azathioprine inhibits purine synthesis, an essential step in the proliferation of white cells and has a half-life of around 5 hours.

According to latest NICE guidelines, patients with isolated atrial septal defects do not require prophylactic antibiotics originally used in prevention of infective endocarditis in dental procedures.

Class I indications (i.e., the benefit greatly outweighs the risk, and the treatment should be administered): -Structural heart disease, sustained VT
-Syncope of undetermined origin, inducible VT or VF at electrophysiologic study (EPS)
-Left ventricular ejection fraction (LVEF) ≤35% due to prior MI, at least 40 days post-MI, NYHA class II or III
-LVEF ≤35%, NYHA class II or III
-LVEF ≤30% due to prior MI, at least 40 days post-MI
-LVEF ≤40% due to prior MI, inducible VT or VF at EPS

Class IIa indications (i.e., the benefit outweighs the risk and it is reasonable to administer the treatment):
-Unexplained syncope, significant LV dysfunction, nonischaemic cardiomyopathy
-Sustained VT, normal or near-normal ventricular function
-Hypertrophic cardiomyopathy with 1 or more major risk factors
-Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) with 1 or more risk factors for sudden cardiac death (SCD)
-Long QT syndrome, syncope or VT while receiving beta-blockers
-Nonhospitalized patients awaiting heart transplant
-Brugada syndrome, syncope or VT
-Catecholaminergic polymorphic VT, syncope or VT while receiving beta-blockers
-Cardiac sarcoidosis, giant cell myocarditis, or Chagas disease

L4 dermatome distribution includes the kneecaps.

Carbon monoxide (CO) poisoning, considered as the great imitator of other diseases, as the patients present with a myriad of symptoms. The carbon monoxide diffuses rapidly across the pulmonary capillary membrane binding to the haem molecule with a very high affinity (240 times that of oxygen) forming carboxy-haemoglobin (COHb). Non-smokers have a baseline COHb of ,3% while smokers have a baseline COHb of 10-15%.

Use of Hyperbaric oxygen therapy (HBOT) for treatment of mild to moderate CO poisoning is not routine.
The selection criteria for HBOT in cases of CO poisoning include:
• COHb levels > 20-25%
• COHb levels > 20% in pregnant patient
• Loss of consciousness
• Severe metabolic acidosis (pH <7.1)
• Evidence of end-organ ischemia (e.g., ECG changes, chest pain, or altered mental status)
Principle of HBOT:
Exposing patients to 100 percent oxygen under supra-atmospheric conditions results in a decrease in the half-life (t1/2) of COHb, from , 90 min in atmospheric air to , 30 minutes. The amount of oxygen dissolved in the blood also rises from , 0.3 to 6 mL/dL, increasing the delivery of non-haemoglobin-bound oxygen to the tissues.

Here, the patient seems to be intolerant to standard metformin. In such cases, modified-release preparations is considered as the most appropriate next step.
There is some evidence that these produce fewer gastrointestinal side-effects in patients intolerant of standard-release metformin.

Metformin is a biguanide and reduces blood glucose levels by decreasing the production of glucose in the liver, decreasing intestinal absorption and increasing insulin sensitivity.
Metformin decreases both the basal and postprandial blood glucose.
Other uses: In Polycystic Ovarian Syndrome (PCOS), Metformin decreases insulin levels, which then decreases luteinizing hormone and androgen levels. Thus acting to normalize the menstruation cycle.

Note:
Metformin is contraindicated in patients with severe renal dysfunction, which is defined as a glomerular filtration rate (GFR) less than 30 ml/min/1.732m2.
Metformin overdose has been associated with hypoglycaemia and lactic acidosis, for this reason, it has a black box warning for lactic acidosis.

Gaucher’s disease is characterized by hepatosplenomegaly, cytopenia, sometimes severe bone involvement and, in certain forms, neurological impairment. The variability in the clinical presentations of GD may be explained by the continuum of phenotypes. However, three major phenotypic presentations can usually be distinguished. Type-1 GD is usually named non-neuronopathic GD; type-2 and type-3 are termed neuronopathic-GD. Gaucher disease (GD, ORPHA355) is a rare, autosomal recessive genetic disorder. It is caused by a deficiency of the lysosomal enzyme, glucocerebrosidase, which leads to an accumulation of its substrate, glucosylceramide, in macrophages.

A history of ischaemic heart disease in a contraindication for prescribing triptans because they act by constricting cerebral and also coronary vessels, increasing the risk of stroke.

Benign Prostatic Enlargement or Hyperplasia (BPE/BPH) is the most probable diagnosis of the patient in question. It is a histological diagnosis characterized by proliferation of the cellular elements of the prostate.
The initial treatment modality of choice is selective alpha 1 antagonists (such as Prazosin, Alfuzosin and Indoramin, and long acting agents like, Terazosin, Doxazosin, etc.) as they provide immediate relief from the bothersome lower urinary tract symptoms (LUTS).
Other treatment modalities include:
• Non-selective alpha blockers: no longer used due to severe adverse effects and the availability of selective alpha 1 blockers.
• 5 alpha reductase inhibitors: Finasteride and Dutasteride, they target the underlying disease process and reduce the overall prostate volume. Thus, reduce the urinary retention and the lower urinary tract symptoms. (They do not provide immediate relief from LUTS and thus are not preferred as first line drugs over alpha 1 antagonists)
• PDE-5 Inhibitors: The long-acting tadalafil has proven to be useful.
• Surgical Treatment modalities: TURP, Prostatectomy, etc.

Type I interferons (IFNs) form a network of homologous cytokines that bind to a shared, heterodimeric cell surface receptor and engage signalling pathways that activate innate and adaptive immune responses.