A drug with a volume of distribution of 200 L and a clearance of 50 L/h is given as a single IV bolus dose. Calculate the half-life of this drug.

• A 2.77 hours ✓
• B 4.0 hours
• C 1.39 hours
• D 5.5 hours

Explanation

Half-life (t½) = 0.693 × Vd / CL = 0.693 × 200 L / 50 L·h⁻¹ = 0.693 × 4 h = 2.77 hours. This is the standard first-order elimination formula. A large Vd relative to clearance lengthens the half-life; halving clearance would double the half-life, which is clinically relevant in hepatic or renal impairment where clearance decreases.

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

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