For CrCl < 60 mL/min, which drug should have its dose reduced due to CNS adverse effects?

• A. Gabapentin
• B. Atorvastatin
• C. Metformin
• D. Albuterol

Answer: (A)

Renal impairment can lead to accumulation of drugs cleared by the kidneys, increasing adverse effects. Gabapentin is eliminated almost entirely by the kidneys, so when CrCl is below 60 mL/min its clearance drops and drug levels rise. Higher gabapentin levels amplify CNS effects such as dizziness, somnolence, confusion, and ataxia, making dose reduction appropriate in this setting. The other drugs listed are not predominantly limited by renal clearance in a way that would cause CNS effects at this CrCl threshold: atorvastatin is mainly hepatically cleared and not typically dose-adjusted for CNS risk in this context; metformin’s main concern with reduced renal function is lactic acidosis rather than CNS effects; and albuterol, an inhaled bronchodilator, has minimal CNS impact and does not require adjustment for this renal measure.