A new drug has a volume of distribution of 100 L and systemic clearance of 10 L/hour in an average adult. Its elimination half-life is most closely approximated by:
- A 3.5 hours
- B 7 hours ✓
- C 10 hours
- D 14 hours
Correct answer: B. 7 hours
Explanation
Half-life is calculated as t1/2 = 0.693 x Vd / CL. Substituting values gives 0.693 x 100 / 10 = 6.93 hours, roughly 7 hours. Option C confuses clearance units with half-life, while option D results from using 1.44 instead of 0.693 or doubling the answer. This relationship shows that half-life depends jointly on both distribution and clearance, neither parameter alone.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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