Characterization studies of solid-state forms of allopurinol

Allopurinol is a Class IV drug by the Biopharmaceutical Classification System. Considering that each solid-state form of drug may have different physicochemical properties, studies of different solid-state forms are important in the field of pharmaceutical sciences. The aim of this work was to obtain distinct solid-state forms of allopurinol and to characterize them. Allopurinol hydrochloride was obtained by recrystallization from anhydrous raw material, in which these two solid-state forms were studied by characterization techniques, shake flask solubility, intrinsic dissolution and accelerated stability studies. Solubility and intrinsic dissolution studies have shown that allopurinol hydrochloride is statistically more soluble at 37°C at pH 4.5 and 5.4 and has a higher intrinsic dissolution rate than the anhydrous form, and both solids are stable after 6 months of study. In conclusion, it is of great importance in the area of pharmaceutical sciences to study new solid-state forms that can present better bioavailability data.