A drug has a volume of distribution of 40 L and a clearance of 8 L/h. What is its elimination half-life?
- A 2.0 hours
- B 5.0 hours
- C 3.5 hours ✓
- D 6.9 hours
Correct answer: C. 3.5 hours
Explanation
Elimination half-life is calculated as t½ = 0.693 × Vd / CL. Here, t½ = 0.693 × 40 L / 8 L/h = 0.693 × 5 h = 3.465 h ≈ 3.5 h. The volume of distribution reflects drug distribution in body tissues relative to plasma, and clearance reflects the volume of plasma cleared per unit time. A higher Vd with the same clearance prolongs half-life, while higher clearance with the same Vd shortens it.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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