Acetylsalicylic acid × Gentamicin

Additive nephrotoxicity. Aspirin suppresses prostaglandin-dependent renal blood flow (at high doses); gentamicin causes direct tubulotoxicity.

Reduced urine output, rising creatinine. Symptoms appear earlier in older patients and chronic kidney disease.

Cardioprotective aspirin doses (75–100 mg) do not require withdrawal. At high doses, check creatinine before and 3–5 days into gentamicin therapy. Ensure adequate hydration; consider switching to a less nephrotoxic antibiotic (a cephalosporin, carbapenem).