A drug has a volume of distribution of 40 L and an elimination half-life of 8 hours. Its clearance (in L/h) is approximately:

• A 320 L/h
• B 0.35 L/h
• C 3.5 L/h ✓
• D 5.0 L/h

Explanation

Clearance = (0.693 × Vd) / t1/2 = (0.693 × 40 L) / 8 h = 27.72 / 8 = 3.465 L/h ≈ 3.5 L/h. This value represents the volume of plasma cleared of drug per unit time. The relationship CL = Vd × ke (where ke = 0.693/t1/2) is the fundamental link between distribution, elimination half-life and clearance in a one-compartment model. The other options do not satisfy this calculation.

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

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