Pharmacokinetics and Pharmacodynamics · USMLE Step 1

If a drug displays first-order elimination kinetics, what happens to the amount eliminated per unit time as plasma concentration decreases?

  1. Remains constant
  2. Decreases
  3. Increases
  4. Stops
Show answer and explanation

Correct answer: Decreases

In first-order kinetics elimination is proportional to concentration; thus as concentration decreases, the amount eliminated per unit time decreases.

Difficulty: Medium Question 17 of 20

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