The effect of increased lipoprotein levels on the pharmacokinetics of ketoconazole enantiomers in the rat.

(±)-Ketoconazole (KTZ) is a chiral antifungal drug that inhibits cytochrome P450 (CYP)-mediated metabolism of other drugs. Because of its lipophilicity, KTZ pharmacokinetics might change in elevated plasma lipoprotein concentrations. To explore that, the stereoselective pharmacokinetics of KTZ were assessed in a rodent model of hyperlipidaemia (HL). Rats were given KTZ intravenously (i.v.) or orally. Serial blood samples were collected over 24 h for the iv dosed groups. After oral doses, plasma and liver specimens were obtained up to 6 h after dosing. All specimens were assayed using stereospecific assay. Orally and iv dosed rats showed no significant differences between normolipidemic and hyperlipidaemic area under the plasma concentrations vs. time curves or clearance (CL), of both KTZ enantiomers. In iv dosed rats, however, the volume of distribution (V(ss)) was significantly higher in HL for both enantiomers. The (+):(-) KTZ ratios of CL and V(ss) were also higher in hyperlipidaemic rats. After oral doses, the liver to plasma concentration ratios of (-)-KTZ (but not antipode) were significantly lower in HL. In conclusion, HL caused an increase in V(ss), and possibly decreased liver uptake of the more potent CYP-inhibiting (-) enantiomer.