A new drug has a total body clearance of 7 L/h and a volume of distribution of 70 L in an average adult. What is its elimination half-life?
- A Approximately 7 hours ✓
- B Approximately 3.5 hours
- C Approximately 10 hours
- D Approximately 14 hours
Correct answer: A. Approximately 7 hours
Explanation
Half-life equals 0.693 multiplied by Vd divided by clearance: 0.693 x 70/7 = 6.93 hours, approximately 7 hours. This relationship shows that half-life is a derived parameter depending on both Vd and clearance, not an independent property. Option D would result if the 0.693 factor were omitted incorrectly or the arithmetic doubled; option B results from dividing clearance by Vd without the 0.693 constant.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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