Which statement accurately describes first-order kinetics of drug elimination?

• A A constant amount of drug is eliminated per unit time
• B The half-life increases as the plasma concentration increases
• C Most drugs at therapeutic doses follow zero-order kinetics
• D The elimination rate is proportional to the plasma concentration ✓

Explanation

In first-order kinetics, a constant fraction of the drug is eliminated per unit time. Therefore, the rate of elimination is directly proportional to the plasma drug concentration. The half-life remains constant regardless of the dose. Option A describes zero-order kinetics, where a constant amount is eliminated per time. Option C is false because most drugs follow first-order kinetics at therapeutic doses, only switching to zero-order at toxic or saturated levels.

Reference: Katzung Basic and Clinical Pharmacology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.