Solubility of sildenafil citrate in mixed water-cosolvent

Abstract

Solubility is one of the important phenomenon in pharmaceutical sciences and cosol-vency is a common method for increasing solubility. Cosolvency recognized that the adding of an organic cosolvent to water and it can modify the solubility of drugs. There are some models for predicting solubility and Jouyban-Acree is one of the ac-ceptable model to predict solubility in solvent mixture. Aim: We aimed to investigate solubility of sildenafil citrate (SC) in water+cosolvent mix-ture and prediction of solubility with cosolvency models. Materials and Methods: One of the ordinary methods to determine solubility of drug is Higuchi and Connors shake-flask technique. An excess amount of drug was added to glass vials containing binary solvent mixtures of cosolvent and water. Samples were placed in an incubator at specified temperature (293.3, 298.3, 303.3, 308.3 and 313.3 K) and allowed to equilibrate. Then they were filtered and aliquots were analyzed at 290 nm and the saturated concentrations were calculated using the calibration curve. The experimental data were fitted to Jouyban-Acree and Jouyban-Acree van’t Hoff models. Results: The solubility data of SC in binary solvent mixtures at different temperatures show that the solubility improves obviously in presence of cosolvent and increasing the temperature. The constants which investigated from Jouyban-Acree model were ap-plied to predict solubility. Conclusion: Results showed that adding of mentioned cosolvents could change the solubility of SC with a non-linear profile. Obtained mean percent deviation values indicate that the Jouyban-Acree model has a good reliability to predict solubility of the SC saturated solutions in various binary solvent mixtures at the studied temperature ranges.