Quality evaluation of the Finasteride polymorphic forms I and II in capsules

•A rapid HPLC method to determination of Finasteride in capsules was validated.•The physicochemical properties of Finasteride polymorphic forms were studied.•Dissolution profile and stability study of Forms I and II capsules were carried out.•A significant influence of polymorphism on the Finasteride properties was observed.•It is suggested that the Finasteride raw material be strictly controlled. Finasteride (FNS) is a specific competitive inhibitor of steroid type-II 5α-reductase and is widely used for the treatment of benign prostatic hyperplasia, prostate cancer, and androgenetic alopecia. FNS has two polymorphic forms identified as Form I and Form II. It is known that polymorphism can cause significant differences in the physicochemical properties of a compound such as melting point, density, morphology, solubility, and color. Thus, proper qualitative and quantitative monitoring of the solid-state forms is crucial to ensure high-quality products. There are no published papers studying the influence of the FNS polymorphs on the physicochemical quality of capsules. Furthermore, the available analytical methods are time-consuming, expensive, use buffer or do not demonstrate stability-indicating capacity. The aim of this work was to validate a rapid high-performance liquid chromatography (HPLC) method to evaluate FNS in capsules and to study the physicochemical properties of polymorphic forms, evaluating their possible influence in the dissolution profile and stability of FNS in capsules. Capsules containing Forms I and II of FNS were prepared and subjected to quality control studies, dissolution profiles and a stability study at 50°C. A significant effect of polymorphism on the FNS solubility and dissolution properties was observed. These results suggest that changes in the effects of FNS can occur if a suitable control study is not performed on the raw material used to produce the capsules.