STUDY OF KINETIC PARAMETERS OF THERMAL DECOMPOSITION OF CILOSTAZOL UNDER ISOTHERMAL AND NON-ISOTHERMAL CONDITIONS

Cilostazol is a drug used to treat the symptoms of intermittent claudicating, which is basically leg pain caused by walking. Thermogravimetry/derivative thermogravimetry and differential thermal analysis are useful techniques that have been successfully applied in the pharmaceutical industry to study the thermal degradation and kinetic parameters; activation energy (Ea), frequency factor (A), and reaction order (n), as regarding the physicochemical properties of drugs and excipient molecules, such as polymorphism, stability, purity, formulation compatibility, among others. The kinetic parameters were evaluated by isothermal and non-isothermal conditions including Ozawa's conventional method, Ozawa?Flynn?Wall and Friedman isoconversional methods. The kinetic parameters were determined using the thermogravimetric curves of the decomposition process. The results of TG analysis revealed that the main thermal degradation for the Cilostazol occurs during two temperature ranges of 175?300 and 300?600 °C. The TG/DTA analysis of Cilostazol indicates that this drug melts (at about 160 °C) before it decompose. The results showed that as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy values obtained were 162.2 and 163.12 kJ mol-1 for the isothermal and non-isothermal conditions, respectively. Finally, the values of ΔS # , ΔH # , and ΔG # of the decomposition reaction were calculated. Key words: Thermal decomposition, Cilostazol, isothermal