Characterization and thermal stability study of efavirenz and solid dispersion with PVPVA 64 by means of thermal analysis and pyrolysis coupled with GC/MS

The acquired immunodeficiency syndrome remains a major problem in worldwide public health and its antiretroviral treatment therapy combines at least three high activity classes of drugs. Access to antiretroviral treatment for HIV-infected patients is a global public health priority and efavirenz (EFZ) is one of the first drug choices. However, EFZ is classified as a class II drug, according to the biopharmaceutics classification system due to low solubility and high permeability, which leads it to fail in absorption and hence bioavailability. One of the approaches used to overcome these issues is the preparation of solid dispersions. In this study, thermal analysis and pyrolysis coupled with gas chromatography-mass spectrometry (GC/MS) were employed to determine efavirenz thermal stability and the solid dispersion with poly (vinylpyrrolidone-co-vinylacetate) (PVPVA 64). Thus, it suggests that EFZ was converted to its amorphous state, and there was an increase in EFZ thermal stability when it is dispersed in a polymer matrix compared to the drug alone, since there was an increase in the activation Energy ( Ea ) and a decrease in frequency factor ( A ). Furthermore, there was a change in the zero reaction order to one. The thermal stability time of the formulation was estimated at 7 months. In addition, it was possible to observe a good correlation between loss of mass and the technique of Pyrolysis-GC–MS and to posit the formation of new fragments, which clarifies the technique with regard to the identification of thermal decomposition fragments.