Study of solubility and thermodynamic properties of sildenafil citrate in the binary mixtures of propylene glycol and isopropanol at different temperatures

Abstract

Considering the low water solubility of most drugs, improving this feature is one of the important steps in drug research and development. One of the simplest and oldest methods of increasing solubility is cosolvency. In addition, to predict solubility in different solvent systems, in order to save time and money, modeling with various mathematical models can be used.Aim:In the present study, the solubility and density of the sildenafil citrate in the mixture of propylene glycol + isopropanol solvents were investigated in the temperature range of 293.2 to 313.2 K. Also, the correlations between measured data and different solubility models have also been investigated.Method: In the present study, the solubility is measured using shake-flask method. In this way, mass fractions of propylene glycol and isopropanol were prepared at 10% mass intervals, and the excess amount of drug is dispensed into it, and after centrifuging the solution and proper dilution, the absorbance of the solutions was read by a UV spectrophotometer at a wavelength of 290 nm, and the concentration of the samples is obtained by referring to the calibration curve. This process is repeated for 5 temperatures and all data are correlated in some common cosolvency models.Results: Based on the obtained data, the solubility increases with the increase of the mass fraction of propylene glycol and the temperature, so that the maximum solubility is related to the mass fraction of 0.9 of propylene glycol at a temperature of 313.2 K. Conclusion :Solubility data showed an upward trend with temperature increasing and the increase in mass fraction of propylene glycol solvent up to 0.9. The obtained data were represented with different models and the constants of each model were calculated.