A drug is to be given by continuous IV infusion to maintain an average steady-state plasma concentration of 2 mg/L. Its clearance is 5 L/h. What infusion rate is required?

• A 20 mg/h
• B 10 mg/h ✓
• C 5 mg/h
• D 2.5 mg/h

Explanation

At steady state, the rate of drug input equals the rate of elimination, so dosing rate = CL x Css. Here 5 L/h x 2 mg/L = 10 mg/h. The key insight tested is that the maintenance infusion rate is independent of Vd; Vd determines only how long steady state takes to reach and what loading dose would be needed. Students who incorrectly use Vd in this calculation arrive at the wrong options.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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