A drug is given IV at a rate of 20 mg/hour. Its clearance is 5 L/hour. What is the expected steady-state plasma concentration (Css)?

• A 4 mg/L ✓
• B 100 mg/L
• C 0.25 mg/L
• D 10 mg/L

Explanation

At steady state, the rate of drug input equals the rate of drug elimination. Css = Infusion rate / Clearance = 20 mg/hr ÷ 5 L/hr = 4 mg/L. This relationship is fundamental — steady-state concentration is directly proportional to dose rate and inversely proportional to clearance, independent of volume of distribution. The time to reach steady state depends on half-life, not on dose rate or clearance directly.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.