A new drug is being characterized. Its rate of elimination declines proportionally as its plasma concentration falls, and its half-life remains the same whether 10 mg or 100 mg is administered. This drug follows:
- A Zero-order kinetics
- B First-order kinetics ✓
- C Michaelis-Menten saturable kinetics
- D Capacity-limited kinetics
Correct answer: B. First-order kinetics
Explanation
In first-order kinetics the elimination rate is directly proportional to plasma concentration, so a constant fraction of drug is removed per unit time and the half-life is independent of dose. A constant amount removed per unit time defines zero-order kinetics, where the eliminating system is saturated; such drugs show a dose-dependent half-life and disproportionate rise in levels when dose is increased.
Reference: Katzung Basic and Clinical Pharmacology, 16th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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