Tabriz University of Medical Sciences Advanced Pharmaceutical Bulletin 2228-5881 5 4 2015 11 30 Thermal Analysis Investigation of Dapoxetine and Vardenafil Hydrochlorides using Molecular Orbital Calculations 523 529 10.15171/apb.2015.071 EN Ali Kamal Attia Eglal R. Souaya Ethar A. Soliman Journal Article 10.15171/apb.2015.071 2015 05 20 2015 07 30 Purpose: Thermal analysis techniques have been used to study the thermal behavior of dapoxetine and vardenafil hydrochlorides and confirmed using semi-empirical molecular orbital calculations. Methods: Thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis and differential scanning calorimetry were used to determine the thermal behavior and purity of the drugs under investigation. Thermodynamic parameters such as activation energy, enthalpy, entropy and Gibbs free energy were calculated. Results: Thermal behavior of DAP and VAR were confirmed using by semi-empirical molecular orbital calculations. The purity values were found to be 99.97% and 99.95% for dapoxetine and vardenafil hydrochlorides, respectively. The purity of dapoxetine and vardenafil hydrochlorides is similar to that found by reported methods according to DSC data. Conclusion: Thermal analysis justifies its application in quality control of pharmaceutical compounds due to its simplicity, sensitivity and low operational costs.