Physico-chemical characterisation of different solid forms of spironolactone

Spironolactone is a steroidal diuretic showing incomplete oral behaviour because of its low solubility and slow dissolution rate. Four solid forms were obtained by recrystallisation of a commercial sample from different solvents (acetone, methanol, ethyl acetate). These samples have been characterised by Fourier transform infrared (FT-IR) Spectroscopy, X-ray powder diffraction, thermogravimetric analysis coupled with FT-IR spectroscopy (TG/FT-IR) and differential scanning calorimetry (DSC). The aim of the work is establish evidence for differences, if any, between the forms and, possibly, to understand their nature. A careful analysis of the collected data makes it possible to rule out the presence of any solvate and to distinguish three different polymorphs.