Pharmacology and Clinical Therapeutics
Pharmacology and Clinical Therapeutics tests pharmacokinetics, adverse drug reactions, interactions, and rational prescribing. The exam favors practical safety: renal dosing, pregnancy, and common interactions.
Core rules
- Warfarin is monitored by INR; many antibiotics inhibit CYP2C9 and raise INR.
- Avoid ACE inhibitors and ARBs in pregnancy; avoid metformin in severe renal impairment.
- Aminoglycosides and vancomycin need dose adjustment and monitoring in renal impairment.
- Antibiotic de-escalation should follow culture results; do not stop effective therapy merely because the patient improves early.
Worked example
A patient stable on warfarin is prescribed cotrimoxazole for a urinary tract infection. Cotrimoxazole inhibits CYP2C9 and can displace warfarin from protein binding, raising INR and bleeding risk. Check INR within a few days, consider an alternative antibiotic, and adjust the warfarin dose. Do not simply continue both without monitoring.
Traps
- Prescribing full-dose renally cleared drugs without checking eGFR.
- Assuming a penicillin allergy is lifelong and avoiding all beta-lactams without assessment.
- Missing enzyme-inducing interactions that lower contraceptive efficacy.
- Treating a drug rash with another drug from the same class.