Thermodynamic study of sildenafil citrate dissolution in the cosolvency system of isopropanol + water

Abstract

In drug discovery and development, solubility is one of the important physicochemical properties. Solubility data provide important and useful information for the preparation of drug formulations, the development of drug analysis, recrystallization of the purification process, the properties of the solid phase and extraction. In this project, our aim is thermodynamic study of sildenafil citrate dissolution in the cosolvency system of isopropanol+ water and prediction of solubility data with some cosolvency models. Aims:In this study, Solubility of sildenafil citrate in the binary mixtures of isopropanol + water mixtures at different temperatures ranged from 293.2 to 313.2 K, the calculation of density and thermodynamic parameters, also the study of the correlation of solubility and density data with cosolvency models were investigated.Method:In this study, the shake-flask method has been used. So that at every five temperatures, The excess amounts of solute were poured into volumetric flasks containing a certain mass ratio of cosolvent + solvent and after centrifugation and dilution, a UV-Vis spectrophotometer was employed to read their adsorption at the maximum drug’s wavelength. Then, the concentration of the samples was obtained by referring to the calibration curve and the correlation of the data with cosolvency models was checked.Results :According to the experimental data, the solubility increases with increasing in both isopropanol mass fraction and temperature, so that the highest solubility is obtained in the solvent system related to the mass fraction of 0.6 of isopropanol at 313.2 K. Then , by adding more amounts of cosolvent, the solubility is reduced so that the lowest solubility is related to pure isopropanol at 293.2 K.Conclusion: In this study, the obtained experimental data were correlated with cosolvency models and the constants of each model is reported and discussed in detail.