Pharmacology Pharmacokinetic Principles 5

Question 1

A patient is a CYP2D6 poor metabolizer. What is the most likely clinical consequence when prescribed codeine?

Accepted Answer

Reduced conversion to morphine and diminished analgesia

Answer

Codeine requires CYP2D6 to convert it to active morphine; poor metabolizers produce little morphine and experience inadequate pain relief.

Question 2

Which of the following conditions would most likely INCREASE the free fraction of a highly protein-bound drug?

Accepted Answer

Hypoalbuminemia from liver cirrhosis

Answer

Hypoalbuminemia reduces available binding sites, increasing the unbound (free) drug fraction and risk of toxicity.

Question 3

Tmax in a pharmacokinetic curve refers to:

Accepted Answer

The time at which maximum drug concentration occurs

Answer

Tmax is the time point at which the peak plasma concentration (Cmax) is reached after drug administration.

Question 4

Why is intravenous administration considered the gold standard for 100% bioavailability?

Accepted Answer

IV drugs are delivered directly into systemic circulation with no absorption barrier

Answer

Intravenous administration places drug directly into the bloodstream, completely bypassing absorption and first-pass metabolism.

Question 5

A drug has nonlinear (saturable) pharmacokinetics. Which of the following is expected at supratherapeutic doses?

Accepted Answer

Small dose increases cause disproportionately large increases in plasma levels

Answer

When metabolic enzymes become saturated, small increases in dose cause disproportionate plasma level rises, increasing toxicity risk.

Pharmacology Practice Test