Here are the answers to all 20 pharmacology MCQs from the prefinal examination paper:

1. Low apparent volume of distribution of a drug indicates that: D. Drug is not extensively distributed to tissues A low Vd means the drug stays mostly in the plasma/blood and does not distribute widely into peripheral tissues.

2. Zero order kinetics is followed by all of the following drugs EXCEPT: A. Phenytoin Wait - actually Phenytoin does follow zero-order kinetics at therapeutic doses (saturation kinetics). The drugs that follow zero-order: Phenytoin, Alcohol, Barbiturates, Theophylline (at toxic doses). This question is tricky - Barbiturates (B) typically follow first-order kinetics, making them the exception. Correct answer: B. Barbiturates

3. Which of the following acts through G protein coupled receptors? A. Muscarinic receptors Muscarinic receptors (M1-M5) are classic GPCRs. Nicotinic receptors are ion channels; Insulin receptors are tyrosine kinases; GABA-A receptors are ligand-gated ion channels.

4. Therapeutic index is an assessment of: D. Margin of safety Therapeutic Index = TD50/ED50 - it measures how safe a drug is, i.e., the margin between effective and toxic doses.

5. True about orphan drug is: C. Drugs used for rare diseases Orphan drugs are developed for rare (orphan) diseases affecting small populations. Orphan drug status provides regulatory and financial incentives.

6. Which of the following is a prodrug? B. Enalapril Enalapril is a prodrug converted to enalaprilat (the active form) in the liver. Lisinopril is NOT a prodrug - it is active as ingested. Dopamine does not cross the BBB well but is not a prodrug per se.

7. Anti-glaucoma drug that acts by increasing uveoscleral outflow is: A. Latanoprost Latanoprost is a prostaglandin F2α analogue that increases uveoscleral (alternative) outflow to reduce IOP. Timolol reduces aqueous production; Pilocarpine increases trabecular outflow; Dorzolamide reduces aqueous humor production.

8. Which of the following drugs has NO cycloplegic action? D. Phenylepherine Phenylephrine is a pure alpha-1 adrenergic agonist that causes mydriasis but NO cycloplegia (it does not block the ciliary muscle). Atropine, Cyclopentolate, and Tropicamide all cause both mydriasis AND cycloplegia (they are anticholinergics).

9. Fenoldopam is used in the management of: A. Hypertensive emergencies Fenoldopam is a selective dopamine D1 receptor agonist used for short-term management of severe hypertension/hypertensive emergencies. It also increases renal blood flow.

10. Propranolol is contraindicated in diabetes mellitus because it: C. Masks the hypoglycaemic symptoms Propranolol (non-selective beta-blocker) masks the sympathetic warning signs of hypoglycemia (tachycardia, tremor, palpitations) except sweating. This makes it dangerous in diabetics on insulin.

11. Digibind is used to: C. Treat digoxin toxicity Digibind (digoxin-specific antibody fragments, Fab fragments) binds and neutralizes digoxin in cases of life-threatening digoxin toxicity.

12. Centrally acting antihypertensive drug is: C. Propranolol Wait - Propranolol is not centrally acting. The correct answer is B. Methyl dopa (methyldopa acts centrally as an alpha-2 agonist after conversion to alpha-methylnorepinephrine). Clonidine is also centrally acting but not listed. B. Methyl dopa is correct.

13. With MAO inhibitors, food not given is: D. All of the above (Cheese, Beer, Fish) All tyramine-containing foods (aged cheese, beer, fermented fish) are dangerous with MAO inhibitors due to the "cheese reaction" - hypertensive crisis from accumulated tyramine.

14. Which of the following is an atypical antipsychotic? A. Clozapine Clozapine is the prototype atypical (second-generation) antipsychotic. Chlorpromazine, Thiothixene, and Haloperidol are all typical (first-generation) antipsychotics.

15. Cough is an adverse reaction seen with intake of: C. Enalapril ACE inhibitors (like Enalapril) cause dry, persistent cough due to accumulation of bradykinin and substance P in the lungs. This is a class effect of all ACE inhibitors.

16. Furosemide causes: A. Metabolic alkalosis Furosemide (loop diuretic) causes hypokalemic, hypochloremic metabolic alkalosis due to excessive loss of K+ and Cl-, and increased H+ secretion in the distal nephron.

17. Drug of choice for drug-induced Parkinsonism is: C. Amantadine Drug-induced Parkinsonism (from antipsychotics, metoclopramide, etc.) is best managed with anticholinergics (like trihexyphenidyl/benztropine) or Amantadine. Among the options listed, C. Amantadine is the answer. (Note: Levodopa is avoided as it can worsen psychosis in antipsychotic-induced cases.)

18. Antagonist of benzodiazepine is: B. Flumazenil Flumazenil is the specific competitive antagonist at GABA-A benzodiazepine receptors, used to reverse benzodiazepine overdose/sedation. Naltrexone and Naloxone are opioid antagonists; N-Acetylcysteine is used for paracetamol toxicity.

19. Apixaban is: B. Factor Xa inhibitor Apixaban (along with Rivaroxaban, Edoxaban) is a direct oral Factor Xa inhibitor. Dabigatran is the direct thrombin (Factor IIa) inhibitor. Fondaparinux is an indirect Factor Xa inhibitor. Warfarin is a Vitamin K antagonist.

20. Plasma expanders are used in: B. Severe trauma Plasma expanders (dextrans, hetastarch, albumin, gelatin) are colloidal solutions used to expand intravascular volume in conditions with fluid loss such as severe trauma, hemorrhagic shock, and burns. Severe anemia requires blood transfusion, not plasma expanders.