How should dosing be adjusted in renal impairment?

• A. Lower dose or extend interval proportional to loss of renal clearance.
• B. Increase dose to compensate for decreased clearance.
• C. Switch to hepatic metabolism only.
• D. Use same dose but monitor troughs.

Answer: (A)

Dosing in renal impairment aims to maintain the same drug exposure by accounting for reduced renal clearance. When the kidney’s ability to excrete a drug worsens, clearance drops, half-life lengthens, and overall exposure (AUC) can rise. To avoid toxicity while preserving efficacy, the approach is to lower the dose or extend the dosing interval in proportion to how much renal clearance has declined. This is especially true for drugs that are primarily eliminated by the kidneys. If a drug has significant non-renal clearance or active renal metabolites, adjustments become more nuanced and may require additional monitoring or alternative choices, but the guiding principle remains: match systemic exposure to what would occur with normal kidney function by modifying dose or interval.