Compatibility studies of nevirapine in physical mixtures with excipients for oral HAART

Nevirapine is a hydrophobic non-nucleoside reverse transcriptase inhibitor, used in first line regimens of highly active antiretroviral therapy (HAART). The drug has more than one crystalline form, which may have implications for its behaviour during production and also for its in vivo performance. This study was aimed at exploring the suitability of thermoanalytical methods for the solid-state characterization of commercial crystalline forms of nevirapine. The drug powder was characterized by ultraviolet spectrophotometry, stereoscopy, scanning electron microscopy, wide-angle X-ray diffraction, measurements of density, flowability, solubility and intrinsic dissolution rate (IDR), differential scanning calorimetry, thermogravimetric analysis, and photostability measurements. The results showed that nevirapine has high stability and is not susceptible to degradation under light exposure. The drug showed compatibility with the excipients tested (lactose, microcrystalline cellulose, polyvinylpyrrolidone and polyvinyl acetate copolymer (PVP/PVA), and hydroxypropylmethylcellulose (HPMC)). Nevirapine has low solubility, an acid medium being the most appropriate medium for assessing the release of the drug from dosage forms. However, the data obtained from IDR testing indicate that dissolution is the critical factor for the bioavailability of this drug. Bulk nevirapine powder analysed by scanning electron microscopy and the drug solubility profile in various buffer solutions. The pH values of the media in which the tests were conducted are also presented. [Display omitted] ► Nevirapine shows more than one crystalline form, that influence its in vivo and in vitro behaviour. ► DSC and TGA were used for solid-state characterization of crystalline forms of nevirapine. ► Nevirapine is compatible with lactose, microcrystalline cellulose, PVP/PVA copolymers and HPMC. ► The acid form of nevirapine is the most appropriate for assessing release profile from dosage forms.