The comparative bioavailability of a generic and the innovator fluconazole preparations in healthy Thai volunteers.

We studied the pharmacokinetics and compared the oral bioavailability of the "generic" (Biozole, Biolab Company, Thailand) and the "innovator" (Diflucan, Pfizer Incorporation, U.S.A.) fluconazole preparations in 12 healthy Thai volunteers. A 200 mg single oral dose of each preparation was given to the subjects in a randomized double-blind 2-period crossover design with 2 weeks washout period. Blood samples were collected just before and at 0.5, 1, 2, 2.5, 3, 4, 24, 48, 56 and 72 hours after drug administration. Serum fluconazole concentrations were determined by using high performance liquid chromatography. Individual concentration-time profiles and the pharmacokinetic parameters were analyzed by the noncompartmental pharmacokinetic method [TOPFIT, a pharmacokinetic data analysis program]. The pharmacokinetic parameters (Tmax, Cmax, Vd, Cl) of fluconazole in Thai healthy volunteers were comparable to those values observed in Caucasian subjects. The relative bioavailability of the generic Biozole was 102.38 +/- 9.79 per cent of Diflucan. The means and 90 per cent confidence intervals (90% CI) of the [Biozole/Diflucan] ratio of AUC0-72, AUC0-inf and Cmax were 1.02 (0.98-1.06), 0.99 (0.95-1.03) and 1.13 (1.03-1.25), respectively. These values were well within the acceptable bioequivalence ranges of 0.8-1.25 proposed by the US FDA. The means and 90 per cent CI of Tmax differences [Biozole-Diflucan] were -0.46 [(-1.03)-(0.12)]. This value was outside the stipulated bioequivalence range of +/- 0.41 h (+/- 20% of the Tmax of the reference formulation). Nevertheless, the Tmax difference was not expected to be related to the differences in safety and efficacy of the drug. Hence, Biozole and Diflucan were bioequivalent with respect to the extent of absorption (AUC), and the Cmax, and could be used interchangeably.