A drug has clearance (CL) of 10 L/hour and a volume of distribution (Vd) of 70 L. Calculate the elimination half-life.
- A 7.0 hours
- B 1.4 hours
- C 4.85 hours ✓
- D 9.8 hours
Correct answer: C. 4.85 hours
Explanation
t½ = (0.693 × Vd) / CL = (0.693 × 70 L) / 10 L/hr = 48.51 / 10 = 4.85 hours. This formula links the three fundamental PK parameters: clearance determines how fast drug is eliminated; Vd determines how much drug is available for elimination; and t½ = 0.693 × Vd/CL. Doubling Vd (e.g., in obesity or edema) doubles t½ without changing clearance.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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