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
Which statement correctly describes the relationship between drug clearance and half-life?
Answer: Half-life is inversely proportional to clearance
Half-life = (0.693 × Vd) / clearance, so half-life is inversely proportional to clearance — higher clearance means shorter half-life.
A patient is a 'poor metabolizer' of CYP2C19. They are prescribed omeprazole. What is the expected outcome compared to an extensive metabolizer?
Answer: Higher omeprazole plasma levels
Poor metabolizers lack functional CYP2C19 and cannot efficiently metabolize omeprazole, leading to higher plasma concentrations and greater acid suppression.
What is enterohepatic recirculation and what is its pharmacokinetic effect?
Answer: Reabsorption of bile-excreted drug from the intestine, prolonging its half-life
Enterohepatic recirculation occurs when biliary-excreted drug is deconjugated in the gut and reabsorbed, extending the drug's effective half-life.
In a two-compartment pharmacokinetic model, the 'alpha phase' of the plasma concentration curve represents:
Answer: Distribution from central to peripheral compartment
The rapid alpha (distribution) phase reflects drug moving from plasma into peripheral tissues; the slower beta phase reflects elimination.
A drug has 99% plasma protein binding. A second drug displaces it, reducing binding to 98%. What happens to free drug concentration?
Answer: Doubles (increases by 100%)
Free drug increases from 1% to 2% of total drug — a doubling of the free fraction — which can significantly increase pharmacological effect.
Which route of administration completely bypasses first-pass metabolism?
Answer: Sublingual
Sublingual administration allows drug absorption directly into systemic circulation via the buccal mucosa veins, bypassing portal circulation entirely.
Why do neonates have a higher volume of distribution for water-soluble drugs compared to adults?
Answer: Neonates have a higher proportion of total body water
Neonates have approximately 75-80% total body water (vs. 60% in adults), increasing the Vd of hydrophilic drugs relative to body weight.