Three isostructural solvates of finasteride and their solid-state characterization.

Three crystalline hemi-hydrate, channel solvates (classified as solvates from here on) of finasteride (N-(1,1-di-methylethyl)-3-oxo-4-aza-5 alpha-androst-1-ene-17beta-carboxamide) have been obtained and fully characterized. The acetone, methyl ethyl ketone (MEK), and toluene solvates of finasteride, described herein, were found to be isostructural and belong as additional members to a family of previously reported finasteride solvates. Vacuum drying at 85 degrees C for 1 day produced the metastable, anhydrous Form II of finasteride from all three solvated materials.