Pharmacology and Pharmacotherapeutics
Core Concepts
Safe prescribing requires linking pharmacokinetics (absorption, distribution, metabolism, excretion) to patient factors. Hepatic metabolism via cytochrome P450 informs drug interactions; renal clearance informs dosing adjustments. Know the high-yield interactions: warfarin with antibiotics or amiodarone, MAO inhibitors with sympathomimetics, and QT-prolonging combinations. Understand first-line therapy for common conditions: metformin for type 2 diabetes, ACE inhibitors or ARBs for hypertension with proteinuria, statins for secondary prevention, and inhaled corticosteroids plus bronchodilators for persistent asthma.
Traps to Watch
Questions often test contraindications and monitoring rather than mechanisms. ACE inhibitors cause angioedema and are contraindicated in pregnancy; ARBs are the usual substitute but are also avoided in pregnancy. Beta-blockers can mask hypoglycemia symptoms in diabetics. NSAIDs raise risk in heart failure and CKD. Look for the "which requires monitoring" stem: ACE inhibitors need potassium and creatinine checks; warfarin needs INR; aminoglycosides need renal and hearing monitoring. Do not confuse adverse effects with allergies.
Worked Example
A patient on warfarin develops a urinary tract infection and is prescribed trimethoprim-sulfamethoxazole. Trap answer: "no change needed." Correct reasoning: this antibiotic potentiates warfarin and raises INR and bleeding risk; choose an alternative or monitor closely. Rule of thumb: whenever adding a drug to warfarin, ask about interaction and plan an INR check.