Pharmacology and Clinical Pharmacology
Pharmacology and Clinical Pharmacology tests pharmacokinetics, rational prescribing, adverse reactions, interactions, and stewardship. The exam often asks what to monitor and when to avoid a drug.
Core rules
- Absorption, distribution, metabolism, and excretion determine onset and duration; renal and hepatic impairment change dosing.
- Loading dose fills volume of distribution; maintenance dose matches clearance.
- CYP inhibitors such as macrolides and azoles raise substrate levels; inducers such as rifampicin and carbamazepine lower them.
- Aminoglycosides, vancomycin, digoxin, and warfarin require therapeutic or toxicity monitoring.
- Antimicrobial stewardship: choose agent by site, severity, culture, and local resistance; review at 48–72 hours.
Worked example
A patient on warfarin develops an INR of 6.0 without bleeding after starting clarithromycin. The reasoning: clarithromycin inhibits warfarin metabolism, raising INR. Withhold warfarin, consider vitamin K according to protocol, monitor INR, and avoid the interacting antibiotic if possible. The next prescription should use a non-interacting alternative.
Traps
Do not double a maintenance dose after a missed dose; do not prescribe NSAIDs in renal impairment or peptic ulcer; do not assume a rash is antibiotic allergy without timing.