Pharmacokinetics and Drug Metabolism Flashcards
7 cards from real Pharmacology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacokinetics and Drug Metabolism flashcards as text
A drug's AUC (area under the curve) after intravenous administration is 200 mg·h/L, and after oral administration it is 120 mg·h/L at the same dose. What is the oral bioavailability?
Answer: 60%
Bioavailability (F) = AUC(oral) / AUC(IV) = 120/200 = 0.60, or 60%.
Which condition most likely causes accumulation of drugs eliminated by renal excretion, requiring dose adjustment?
Answer: Chronic kidney disease
Reduced GFR in chronic kidney disease impairs elimination of renally cleared drugs, causing accumulation and potential toxicity without dose reduction.
What is the pharmacokinetic basis for using a maintenance dose rather than repeated loading doses?
Answer: Maintenance doses replace drug eliminated since the last dose, keeping steady state
Maintenance dosing replaces the amount of drug cleared between doses, maintaining steady-state plasma concentrations within the therapeutic window.
Grapefruit juice inhibits intestinal CYP3A4. Which effect would be expected for a drug metabolized by CYP3A4?
Answer: Increased bioavailability due to decreased gut metabolism
Grapefruit juice inhibits intestinal CYP3A4, reducing first-pass metabolism of susceptible drugs and increasing their systemic bioavailability.
A patient with severe hepatic failure is prescribed a drug that undergoes extensive hepatic metabolism. Which pharmacokinetic change is most expected?
Answer: Increased half-life due to reduced clearance
Hepatic failure reduces metabolic clearance, prolonging the half-life and increasing drug accumulation risk.
Which term describes the irreversible loss of drug from the body through all elimination pathways combined?
Answer: Total body clearance
Total body clearance is the sum of all clearance processes (hepatic + renal + other), representing the volume of plasma completely cleared of drug per unit time.
N-acetylation polymorphism classifies patients as slow or fast acetylators. Slow acetylators taking isoniazid are at greatest risk for which adverse effect?
Answer: Hepatotoxicity from acetylhydrazine accumulation
Slow acetylators accumulate isoniazid, which is then metabolized by an alternate pathway to acetylhydrazine, a hepatotoxic metabolite.