Pharmacology Pharmacokinetics and Drug Metabolism 3

Question 1

Which factor most directly determines whether a drug undergoes glomerular filtration in the kidney?

Accepted Answer

Degree of plasma protein binding

Answer

Only the free (unbound) fraction of a drug is filtered at the glomerulus; protein-bound drug cannot pass through the filtration barrier.

Question 2

A weakly acidic drug (pKa 4.5) is in an alkaline urine environment (pH 8). What happens to its renal excretion?

Accepted Answer

Increased, because the ionized form is trapped in tubular urine

Answer

In alkaline urine, weak acids are predominantly ionized, preventing tubular reabsorption and increasing urinary excretion (ion trapping).

Question 3

What is the primary consequence of inhibiting CYP2D6 with fluoxetine in a patient taking codeine?

Accepted Answer

Decreased conversion of codeine to morphine

Answer

CYP2D6 converts codeine to its active metabolite morphine; inhibition by fluoxetine reduces morphine formation, decreasing analgesic efficacy.

Question 4

During pregnancy, increased plasma volume and renal blood flow alter drug pharmacokinetics. Which parameter is most likely to increase for a renally cleared drug?

Accepted Answer

Renal clearance

Answer

Increased GFR and renal blood flow during pregnancy enhance renal clearance of drugs eliminated by the kidneys.

Question 5

An elderly patient has reduced hepatic blood flow. Which class of drugs will show the greatest increase in bioavailability when given orally?

Accepted Answer

High-extraction-ratio drugs

Answer

High-extraction drugs depend on hepatic blood flow for clearance; reduced flow decreases first-pass metabolism and increases oral bioavailability.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Pharmacokinetics and Drug Metabolism 3