Fluconazole–excipient compatibility studies as the first step in the development of a formulation candidate for biowaiver

The biowaiver of bioequivalence studies on class I drugs of the biopharmaceutics classification system (BCS) is aimed mainly at reducing the costs and the exposure of health volunteers to a new pharmaceutical formulation. Fluconazole is an important antifungal agent but in the literature it is not clear whether it belongs to BCS class I or III. Compatibility studies are considered to be the first step in product development and on considering a biowaiver candidate these gain even greater importance since the final product will not be submitted to in vivo tests. The aim of this study was to qualitatively determine the composition of a commercially available fluconazole formulation in the form of capsules with regard to the presence of critical excipients and to carry out compatibility studies by differential scanning calorimetry (DSC). One formulation did not contain sodium lauryl sulfate and contained mannitol, in contrast to the reference formulation, which could hinder the acceptance of the biowaiver. The interaction of fluconazole with microcrystalline cellulose and calcium hydrogen phosphate dihydrate was observed; however, no indication of incompatibility was found in the DSC analysis of the commercial pharmaceutical formulations. These interactions were also studied by Fourier transform infrared spectroscopy, where small changes in the bands were observed, and by X-ray Powder diffraction and scanning electron microscopy that did not evidence any modification in the solid state characteristics.