It is well established that solid-state properties such as solubility, particle size, and morphology are critical factors in the development of pharmaceutical formulations. Thus, the evaluation of the physical-chemical properties of the substances that will be used must be the primary step for quality control in the pharmacy industry. The aim of this report is to characterize and to establish the quality of four spironolactone raw samples, derived from distinct laboratories, through thermal analysis (DSC and TG), infrared spectroscopy (IV), solubility assay, scanning electron microscopy, and digital image analysis. Capsules of spironolactone were also prepared with these different drug samples and dissolution profiles determined. The IR and the DSC assays confirmed the identity of the samples as spironolactone. Morphological differences relating to shape, size, and particle size distribution were found and can be directly related to the varied dissolution profiles presented by the different formulations.