Kinetic study for solid-state degradation of mental disorder therapeutic agents

Abstract

This paper describes the thermal investigations and kinetic analysis regarding the solid-state degradation of three compounds used as mental disorder therapeutic agents (antidepressants), namely amitriptyline, desipramine and imipramine. The study was carried according to ICTAC 2000 recommendations, by using three isoconversional methods, namely Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Friedman. The differential method of Friedman indicated multistep degradation, which was later confirmed by the nonparametric kinetic method (NPK). NPK method showed that all three tricyclic antidepressants are degraded by two processes. In terms of apparent activation energies for decomposition, the NPK method indicated 123.4 kJ mol−1 for imipramine, 112.3 kJ mol−1 for desipramine and 82.9 kJ mol−1 for amitriptyline, and the results are in good agreement with the ones suggested by isoconversional methods.