Comparative thermal stability of two similar-structure hypolipidemic agents

Simvastatin (SIM) and lovastatin (LOV) are two important active pharmaceutical ingredients from statin class, prescribed in the treatment of hypercholesterolemia. Our study presents the results obtained by our research group regarding the decomposition of SIM and LOV in oxidative atmosphere, by employing three isoconversional methods, namely Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. The results obtained by Friedman method suggested a multistep degradation, while the ones obtained by Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa suggested a single-step degradation. In order to validate the results, we used the NPK method, which allowed a concrete separation and nature of processes that contributed to the degradation of both statins. NPK method showed that both SIM and LOV are degraded by contribution of two distinctive chemical processes, and the mean values of activation energies are also reported.