Pharmacology and Pharmacotherapeutics
Pharmacology and Pharmacotherapeutics tests the ability to connect drug mechanism, pharmacokinetics, and patient factors to a safe therapeutic decision. The exam favors applied dosing, interactions, and monitoring over isolated receptor names.
Core rules
- Pharmacokinetics describes absorption, distribution, metabolism, and excretion; pharmacodynamics describes what the drug does at its target.
- Therapeutic index separates effective from toxic exposure; narrow-index drugs need monitoring and individualized dosing.
- CYP induction develops over days to weeks, while inhibition can be immediate. P-glycoprotein alters absorption and CNS penetration.
- Renal and hepatic function change dose or interval; active metabolites can prolong effect in renal impairment.
Worked example
A 70-year-old woman weighs 70 kg and has serum creatinine 1.4 mg/dL. Estimate creatinine clearance using Cockcroft-Gault: CrCl = [(140 - age) x weight] / (72 x SCr), multiplied by 0.85 for female sex. That is (70 x 70) / (72 x 1.4) = 4900 / 100.8 = 48.6 mL/min; 48.6 x 0.85 = 41.3 mL/min. For a renally cleared drug labeled 500 mg every 12 hours for CrCl 30-59 mL/min, choose the reduced regimen rather than the full dose, then monitor response and toxicity.
Traps
Do not use serum creatinine alone as a measure of renal function. Do not apply the female adjustment twice. Check whether the equation used actual, ideal, or adjusted body weight. Distinguish adverse effects that are dose-related from idiosyncratic reactions. When asked about interaction timing, state whether the effect is immediate or delayed.