A 55-year-old man with chronic airflow limitation is stabilized on oral theophylline with a target average steady-state concentration of 10 mg/L. His measured theophylline clearance is 3 L/h. If he takes the drug every 6 hours, what maintenance dose should he receive?

• A 45 mg per dose
• B 90 mg per dose
• C 180 mg per dose ✓
• D 360 mg per dose

Explanation

At steady state the rate of administration equals the rate of elimination, giving maintenance dose = clearance x target concentration x dosing interval: 3 L/h x 10 mg/L x 6 h = 180 mg per dose. Volume of distribution determines the loading dose, not the maintenance dose, so a student who confuses the two parameters would calculate a wrong figure based on Vd.

Reference: Katzung Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.