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Half-Life From Vd and Cl — FRCA Primary MCQ

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ModeratePharmacology - General PrinciplesHalf-Life From Vd and ClFRCA Primary

Regarding drug clearance a drug with a clearance of 100 mL/min and a Vd of 50 L has an elimination half-life of approximately:

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Correct answer: E — 5.8 hours

t½ = (0.693 × Vd) / Cl = (0.693 × 50000 mL) / 100 mL/min = 34650 / 100 = 346.5 min ≈ 5.8 hours. This relationship demonstrates that half-life is a derived parameter dependent on both Vd and Cl. Drugs can have identical half-lives but very different Vd and Cl values.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care