A patient with decreased renal clearance due to a cofactor deficiency requires what dosing adjustment to maintain exposure?

• A. Reassess renal clearance and reduce dose or extend dosing interval.
• B. Increase dose to compensate for lower clearance.
• C. Keep the same dose assuming clearance will recover.
• D. Switch to intravenous administration only.

Answer: (A)

When renal clearance drops, the drug stays in the body longer, so exposure (AUC) increases if you keep giving the same dose. To keep exposure the same, you must lower the dose or extend the dosing interval to account for the slower elimination. Reassessing how much clearance is reduced guides how much to adjust. Increasing the dose would raise exposure further, and keeping the same dose assumes clearance recovers, which isn’t assumed here. Switching to intravenous administration doesn’t by itself fix exposure without changing the dose or interval.