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 factor most directly determines whether a drug undergoes glomerular filtration in the kidney?
Answer: Degree of plasma protein binding
Only the free (unbound) fraction of a drug is filtered at the glomerulus; protein-bound drug cannot pass through the filtration barrier.
A weakly acidic drug (pKa 4.5) is in an alkaline urine environment (pH 8). What happens to its renal excretion?
Answer: Increased, because the ionized form is trapped in tubular urine
In alkaline urine, weak acids are predominantly ionized, preventing tubular reabsorption and increasing urinary excretion (ion trapping).
What is the primary consequence of inhibiting CYP2D6 with fluoxetine in a patient taking codeine?
Answer: Decreased conversion of codeine to morphine
CYP2D6 converts codeine to its active metabolite morphine; inhibition by fluoxetine reduces morphine formation, decreasing analgesic efficacy.
During pregnancy, increased plasma volume and renal blood flow alter drug pharmacokinetics. Which parameter is most likely to increase for a renally cleared drug?
Answer: Renal clearance
Increased GFR and renal blood flow during pregnancy enhance renal clearance of drugs eliminated by the kidneys.
An elderly patient has reduced hepatic blood flow. Which class of drugs will show the greatest increase in bioavailability when given orally?
Answer: High-extraction-ratio drugs
High-extraction drugs depend on hepatic blood flow for clearance; reduced flow decreases first-pass metabolism and increases oral bioavailability.
A loading dose is calculated primarily based on which pharmacokinetic parameter?
Answer: Volume of distribution
Loading dose = target concentration × volume of distribution; Vd determines how much drug is needed to achieve the desired plasma level quickly.
Which metabolic reaction converts prodrug enalapril to its active form enalaprilat?
Answer: Hydrolysis
Enalapril is hydrolyzed (an ester bond is cleaved) by intestinal and hepatic esterases to produce the active ACE inhibitor enalaprilat.