The nephrotoxicity and pharmacokinetics of LY 146032 (daptomycin) were studied in an experimental rat model. Nephrotoxicity was assessed by measuring urinary loss of tubular cells and malate dehydrogenase. LY 146032 (10-250 mg/kg daily iv) led to a dose-dependent and reversible increase of cell elimination. The tubulo-toxic threshold dose is stated to be 10 mg/kg daily. Nephrotoxicity induced by LY 146032 can be reduced by coadministration of fosfomycin or D-glucaro-1.5-lactam, and enhanced by combination with tobramycin. LY 146032 accumulated in renal tissue during repeated administration. Electron microscopy revealed histopathological changes in the kidneys. Therefore the nephrotoxic potential of LY 146032 should be taken into consideration in clinical trials.