Pharmacology and Therapeutics

Furosemide is a loop diuretic acting on ascending limb of loop of Henle (not PCT), effective for pulmonary edema in acute decompensated heart failure. It can be given orally or parenteral. It causes HYPOcalcemia (not hyper), hypercalciuria, and hypokalemia.

Palonosetron has the highest affinity and longest duration among 5-HT3 antagonists due to its unique receptor binding properties. Ondansetron, granisetron, and dolasetron are all 5-HT3 antagonists but palonosetron's binding affinity is superior. This translates to extended antiemetic effect.

Bisphosphonates are indicated for hypercalcemia (especially malignancy-associated), osteoporosis prevention/treatment, and bone metastases from various cancers. Vitamin D intoxication requires different management (hydration, steroids, calcitonin), not bisphosphonates which inhibit bone resorption.

Phenytoin follows FIRST-order kinetics at therapeutic doses, not zero-order. Zero-order kinetics occurs at HIGH doses (saturation of metabolism), not low doses. The statement is backwards. Phenytoin does induce microsomal enzymes, shows dose-dependent half-life increase, and is highly protein-bound.

Metformin should be stopped on the day of surgery due to risk of lactic acidosis, especially if the procedure involves contrast dye or may cause hypoperfusion. Beta blockers and calcium channel blockers like amlodipine are generally continued perioperatively to maintain cardiovascular stability. Statins are also typically continued unless specifically contraindicated.

Antihistamines (first-generation) and tricyclic antidepressants cause significant sedation as a side effect due to H1 receptor blockade in the CNS, but this is not their primary therapeutic use. Digitalis and antiarrhythmics primarily affect cardiac conduction. Macrolides and antibiotics are antibiotics with minimal sedative effects.

Thiopentone, midazolam, and zolpidem/zopiclone all act as positive allosteric modulators at the GABA-A receptor complex to produce their sedative-hypnotic effects. Promethazine is a first-generation antihistamine that primarily acts by blocking H1 receptors, not through GABA-A mechanisms.

Triptans like sumatriptan are selective 5-HT1B/1D receptor agonists. They cause cranial vasoconstriction and inhibit trigeminal nerve release of neuropeptides, effectively aborting migraine attacks. They do not act significantly on 5HT-1A, 5HT-1F, or 5HT-3 receptors.

Heparin, aspirin (antiplatelet), and warfarin are all commonly used for thromboprophylaxis in various clinical settings. Antithrombin-III concentrate is primarily used to treat congenital antithrombin deficiency, not for routine thromboprophylaxis. Heparin works by potentiating antithrombin-III, but giving antithrombin-III itself is not standard prophylaxis.

In patients with rheumatic heart disease (RHD), particularly those with mitral stenosis, methylergometrine is contraindicated because it can cause severe hypertension and pulmonary edema. The drug increases systemic vascular resistance and can precipitate acute decompensation in patients with compromised cardiac function. Misoprostol, oxytocin, and carboprost are safer alternatives for managing postpartum hemorrhage in these patients.

Mivacurium is a benzylisoquinolinium neuromuscular blocking agent. Larger doses do speed the onset of action by increasing the concentration gradient. Mivacurium commonly causes histamine release leading to flushing and can cause bronchospasm. However, mivacurium typically causes hypotension (not hypertension) due to histamine release and ganglionic blockade. This makes hypertension the false statement and the correct 'except' answer.

Thiopentone is contraindicated in shock states because it causes significant cardiovascular depression including myocardial depression and vasodilation, which can worsen hypotension. It is indeed contraindicated in porphyrias due to induction of ALA synthase. Thiopentone has cerebroprotective effects by reducing cerebral metabolic rate and intracranial pressure. While sodium carbonate/bicarbonate is added to the formulation, it functions as a buffer/stabilizer rather than primarily as a preservative.

This 40-year-old heavy smoker with epigastric pain and ST elevations in inferior leads is having an acute inferior STEMI (ST-elevation myocardial infarction). The IMMEDIATE therapy is thrombolytic agents (or primary PCI) to reperfuse the coronary artery and salvage myocardium. Aspirin is essential but adjunctive. Pantoprazole treats gastritis, not MI. Beta-blockers are secondary stabilisation, not immediate reperfusion therapy. Time is muscle - thrombolytics within the golden hour.

Heparin is a glycosaminoglycan (sulfated polysaccharide) produced and stored in mast cells. It acts as a potent anticoagulant by enhancing antithrombin activity, inhibiting clotting factors. Hirudin is from leeches, fibrinogen is a clotting protein precursor, and serotonin is another mast cell mediator but not an anticoagulant.

Acetylcholinesterase is the enzyme that rapidly breaks down acetylcholine at synaptic clefts and neuromuscular junctions, terminating its action. This is crucial for proper nerve signaling and muscle function. Acetylcoenzyme-A is involved in metabolism, Acetylcysteine is a mucolytic drug, and Acetyltransferase transfers acetyl groups.