Thermal behavior and decomposition kinetics of efavirenz under isothermal and non-isothermal conditions

Efavirenz (EFV), a non-nucleoside reverse transcriptase inhibitor, was approved for the treatment of human immunodeficiency virus type 1 infection (HIV-1), and it is used in the high activity antiretroviral therapy in association with others drugs as the best choice of treatment in adults and children. EFV was investigated about its thermal behavior, through DSC, TG, and DTG techniques, and the kinetic parameters were evaluated by isothermal and non-isothermal conditions by Ozawa's conventional method and by an isoconversional method proposed by Ozawa-Flynn-Wall. The decomposition process was obtained by thermogravimetric curves to determine the kinetic. EFV was melted at T (peak) = 411.66 K, and the decomposition started at 528.97 K. The activation energy values obtained were 93.24 and 91.58 kJ mol(-1) for the non-isothermal and isothermal conditions, respectively, with the conventional method. The activation energy values obtained by isoconversional method were practically constant, hence the reaction involves a single step.