A drug has a volume of distribution (Vd) of 700 L in a 70 kg patient and a clearance of 7 L/hour. What is its elimination half-life?

• A 100 hours
• B 50 hours
• C 35 hours
• D 69 hours ✓

Explanation

The formula for half-life is t½ = (0.693 × Vd) / CL. Here: t½ = (0.693 × 700 L) / (7 L/hr) = 485.1 / 7 = 69.3 hours ≈ 69 hours. A large Vd with modest clearance results in a prolonged half-life. This scenario resembles drugs like amiodarone that have very high tissue distribution and extended biological half-lives.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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