Which parameter remains constant across different doses in zero-order kinetics?

• A. Half-life
• B. Area Under the Curve
• C. Volume of Distribution
• D. Elimination Rate

Answer: (D)

Zero-order elimination means a fixed amount of drug is removed per unit time, independent of the drug’s concentration. Because of this saturable, rate-limited process, the elimination rate remains the same when you change the dose. That’s why the parameter that stays constant across different doses is the elimination rate (the fixed amount removed per unit time).

peers: The half-life in zero-order kinetics depends on how much drug you started with, so it changes with dose (t1/2 grows as the initial amount increases). The exposure, or AUC, does not stay the same either; under zero-order, AUC grows nonlinearly with dose (not proportional). The volume of distribution is a separate property relating amount to concentration and does not define the constant elimination rate in this scenario.