Determination of polymorphic forms of finasteride by XRPD, FT-IR, and DSC techniques

Abstract

The Identification, characterization and quantification of polymorphic forms are becoming increasingly important within the pharmaceutical industry. A variety of different physical analytical techniques is usually necessary for this task. In this work solid-state techniques, Infrared Fourier transform spectroscopy (FT-IR), X-ray powder diffractometry (XRPD) and Differential scanning calorimetry (DSC) were used to analyze polymorphic purity of crystalline Finasteride, an type II 5α-reductase inhibitor. A series of different mixtures of Form I and II were prepared by geometric mixing and their FT-IR spectra, DSC endotherm and XRD patterns were obtained and analyzed, either alone or combined together. A working range of 0–10% (w/w) of crystal Form II in Form I was established with a detection level of 7.5%. The results demonstrate that XRPD may be successfully used to distinguish between the Finasteride polymorphs and to quantify the composition of binary mixtures of the two.