A drug has a volume of distribution of 50 L, a clearance of 5 L/hour, and is administered as a 100 mg IV bolus. What is the half-life of this drug?
- A 6.93 hours ✓
- B 5 hours
- C 10 hours
- D 14 hours
Correct answer: A. 6.93 hours
Explanation
Half-life (t1/2) = 0.693 × Vd / CL = 0.693 × 50 L / 5 L·h−1 = 0.693 × 10 h = 6.93 hours. The initial plasma concentration after the 100 mg IV bolus = Dose/Vd = 100 mg/50 L = 2 mg/L. Steady-state is reached after approximately 5 half-lives (~34.65 hours). The formula t1/2 = 0.693 × Vd/CL applies to drugs with first-order elimination kinetics.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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