Influence of Solid Dispersions on the Solubility of Tamsulosin Hydrochloride

Introduction. The solubility rate is a critical aspect of the physicochemical parameters of a pharmaceutical substance that determines the bioavailability profile during the development of a drug formulation. Limited solubility slows down the absorption process and release rates, resulting in insufficient active concentration for a pronounced clinical effect. An innovative solution to improve the pharmacokinetic parameters and therapeutic profile of a substance is the method of "solid dispersions." Solid dispersions of tamsulosin with hydrophilic polymers are a promising direction in the development of new drug formulations with improved characteristics. Objective. To investigate the effect of solid dispersions prepared with polyethylene glycol-1500 (PEG) on the solubility of tamsulosin hydrochloride in aqueous media. Material and methods. The object of the study was tamsulosin hydrochloride. Polyethylene glycol-1500 (PEG-1500) was used as the matrix polymer. Solid dispersions of tamsulosin were prepared by the solvent evaporation method. Results. The developed solid dispersions with tamsulosin increase the solubility and dissolution rate of tamsulosin hydrochloride in water. They enhance the solubility of tamsulosin from PEG-1500-based solid dispersion by 2.92 times compared to the original substance. A comprehensive analysis using various physicochemical methods–UV-spectrophotometry, crystal structure analysis, and optical properties analysis of the Faraday–Kendall effect in the developed solutions-reveals that the increased solubility of tamsulosin from solid dispersions can be attributed to the loss of crystalline structure and the formation of a "solid solution" with the polymer matrix. Upon dissolving the solid dispersion in water, a stable colloidal solution is formed. Conclusion. The solid dispersions obtained with the hydrophilic polymer PEG-1500 facilitate enhanced dissolution of tamsulosin in water. It is planned to utilize these results for developing fast-dissolving drug forms and enteric-coated capsules of tamsulosin with increased bioavailability and controlled release.