Pharmacokinetics and tissue penetration of Sch 39304 in granulocytopenic and nongranulocytopenic rabbits

We studied the plasma pharmacokinetics and tissue penetration of Sch 39304 (SCH), a new antifungal triazole, in granulocytopenic [G(+)] and nongranulocytopenic [G(-)] rabbits. Five female New Zealand White G(-) rabbits were given a single oral dose of 2 mg of SCH per kg of body weight. Levels in plasma, determined by gas-liquid chromatography-electron capture, were obtained for 6 days. This procedure was repeated 2 weeks later with the same rabbits, which were induced and maintained G(+) with cytosine arabinoside. There were no significant differences between the pharmacokinetic parameters of G(+) and G(-) rabbits. Among all animals studied, the maximum concentration of the drug in plasma was 1.4 ± 0.11 μg/ml at 4 ± 0.5 h, the half-life was 25 ± 1.4 h, the volume of distribution at steady state was 3.8 ± 0.3 liters, and the area under the concentration-time curve was 44 ± 3.4 μg · h/ml. SCH was detectable in plasma up to day 6. Levels of SCH in tissue were studied at steady in six G(+) and six G(-) rabbits receiving 2 mg of the drug orally per kg per day for experimental disseminated candidiasis. Tissue SCH levels equalled for exceeded those in plasma (at steady state) at all sites examined, and these ratios were similar in both G(+) and G(-) rabbits. Thus, plasma pharmacokinetics of orally administered SCH were similar for G(+) and G(-) rabbits, and SCH achieved high levels of penetration into multiple tissues, including the liver and the central nervous system.