Pharmacology and Therapeutics: rational drug use and monitoring
What Pharmacology and Therapeutics tests
This domain tests drug classification, mechanism of action, pharmacokinetics, adverse effects, interactions and rational prescribing for common conditions in Nepal. Questions often use a short patient scenario and ask for the best drug, the monitoring parameter or the reason for avoiding a medicine.
Core rules
- Agonists activate receptors; antagonists block them. Efficacy is maximal response, potency is dose needed; a partial agonist can reduce the effect of a full agonist.
- Pharmacokinetics covers absorption, distribution, metabolism and excretion. First-pass metabolism reduces oral bioavailability; renal impairment requires dose adjustment for renally cleared drugs.
- Common serious ADRs: ACE inhibitors cause angioedema and hyperkalaemia; NSAIDs cause GI bleeding and renal impairment; aminoglycosides cause nephrotoxicity and ototoxicity; warfarin causes bleeding.
- Enzyme inhibitors such as macrolides, azoles and valproate raise substrate levels; inducers such as rifampicin, carbamazepine and phenytoin lower them.
- Use the Nepal National List of Essential Medicines and standard treatment guidelines as the prescribing baseline.
Worked example
A 68-year-old on stable warfarin for atrial fibrillation develops a urinary tract infection and is prescribed trimethoprim-sulfamethoxazole. Why is this risky? Trimethoprim inhibits CYP2C9 and can displace warfarin from albumin, raising INR and bleeding risk. The correct action is not simply to continue: check INR, consider an alternative antibiotic based on culture, and if co-administration is unavoidable, monitor INR closely and adjust warfarin dose.
Traps
Confusing prophylaxis with treatment; missing renal dose adjustment; assuming all beta-blockers are safe in asthma; and attributing new symptoms to disease rather than an ADR.