Pharmacokinetics Flashcards
7 cards from real Pharmacy 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 flashcards as text
Which CYP450 enzyme is responsible for metabolizing the largest proportion of clinically used drugs?
Answer: CYP3A4
CYP3A4 is the most abundant hepatic CYP enzyme and is responsible for the metabolism of approximately 50% of all clinically used drugs.
Co-administration of a potent CYP3A4 inhibitor with a CYP3A4 substrate drug would be expected to:
Answer: Increase plasma concentrations of the substrate, raising toxicity risk
A CYP3A4 inhibitor blocks the enzyme responsible for substrate metabolism, causing decreased clearance and elevated plasma concentrations, which can lead to toxicity.
Which of the following is a classic example of a prodrug that requires CYP2C19-mediated hepatic activation for antiplatelet effect?
Answer: Clopidogrel
Clopidogrel is an inactive prodrug converted by CYP2C19 to its active thiol metabolite; poor metabolizers of CYP2C19 have reduced antiplatelet response and increased cardiovascular risk.
In elderly patients, which pharmacokinetic change most commonly leads to drug accumulation and toxicity with renally eliminated drugs?
Answer: Decreased renal clearance (reduced GFR)
GFR declines progressively with age (approximately 1 mL/min/year after age 40), making renally cleared drugs accumulate to higher levels in elderly patients without dose adjustment.
Therapeutic drug monitoring (TDM) of aminoglycosides typically involves measuring which levels?
Answer: Peak and trough serum concentrations
Traditional aminoglycoside TDM measures both peak (for efficacy — concentration-dependent killing) and trough levels (to minimize nephrotoxicity and ototoxicity).
Which of the following drugs is most appropriate for therapeutic drug monitoring due to its narrow therapeutic index?
Answer: Digoxin
Digoxin has a narrow therapeutic index (0.5–2.0 ng/mL) with toxicity (arrhythmias, GI effects) occurring just above therapeutic levels, requiring routine monitoring.
Enterohepatic recirculation of a drug can result in:
Answer: Extended drug half-life by returning drug from bile back to systemic circulation
Enterohepatic recirculation occurs when drug excreted in bile is reabsorbed from the intestine back into portal blood, re-entering systemic circulation and prolonging the drug's half-life and duration of action.