Pharmacokinetics of fluconazole in cats after intravenous and oral administration

Fluconazole (100 mg) was administered to six adult cats as an intravenous infusion over 30 minutes, and the same cats received 100 mg of the drug orally 16 weeks later. The cats were bled repeatedly through an indwelling jugular catheter, the plasma fluconazole concentrations were assayed by high performance liquid chromatography, and the concentration-time data were subjected to a non-compartmental pharmacokinetic analysis. The mean (SD) intravenous half-life (13.8 [2.6] hours) was similar to that observed after oral dosing (12.4 [3.0] hours). The plasma clearances (intravenous 0.9 [0.1], oral 0.9 [0.2] ml min-1 kg-1) and the volumes of distribution at steady state (intravenous 1.1 [0.1], oral 1.0 [0.1] litre kg-1) were also similar after the two routes of dosing. The peak plasma concentration was reached 2.6 hours after oral dosing and the drug was completely bioavailable (1.09 [0.05]). On the basis of this single dose study, the administration of 50 mg fluconazole every eight hours to a 4 kg cat should produce average steady state plasma fluconazole concentrations of approximately 33 mg litre-1.