Ketoconazole and cyclosporine A: combined effects on rat renal function and on serum and tissue cyclosporine A concentration.

The effects of ketoconazole (Kcnz) on cyclosporine A (CyA) serum levels and CyA-nephrotoxicity were studied. To rats later anesthetized with pentobarbital sodium, CyA 12.5 and Kcnz 20 mg/kg/day (n = 20), or CyA 12.5 mg/kg and Kcnz-vehicle (n = 21), was dosed. To rats anesthetized with etomidate (n = 14), CyA 12.5 mg/kg and Kcnz-carrier was dosed. S-CyA was monitored during 14 days, and then the rats were investigated with clearance (C) methods (inulin [(in), lithium (Li)], sodium, and potassium), and liver (L) and kidney (K) CyA was measured. Kcnz increased S-CyA, L-CyA and K-CyA (+50 -80%). There were significant (p less than 0.05) correlations between S- and L- or K-CyA. Kcnz increased CyA nephrotoxicity: Mean Cin was 1.012 ml/min/gKW (kidney weight) after CyA treatment (a subnormal value), but decreased to 0.556 ml/min/gKW in the group also given Kcnz (p less than 0.001). CLi decreased from 0.135 to 0.048 ml/min/gKW (p less than 0.001), and absolute proximal tubular reabsorption decreased from 0.877 to 0.508 ml/min/gKW (p less than 0.001), while the fractional reabsorption in the proximal tubule (FPR), expressed as a percentage of GFR, increased from 86.9 to 91.6% (p less than 0.005). Thus, after Kcnz treatment to rats given CyA 12.5 mg/kg/day, their renal function was indistinguishable from that in rats given CyA 25 mg/kg/day.(ABSTRACT TRUNCATED AT 250 WORDS)