Enhancing the Solubility and Dissolution Performance of Safinamide Using Salts

Safinamide (SAF) is an anti-Parkinson’s disease (PD) drug that has selective monoamine oxidase type-B (MAO-B) inhibition activity. In 2017, SAF was approved by the U.S. Food and Drug Administration (FDA) as safinamide mesylate (SAF-MS, marketed as Xadago). Owing to its poor solubility in water, SAF is a Biopharmaceutics Classification System BCS Class II compound. In this study, four salts of safinamide (with hydrochloric acid (HCl), hydrobromic acid (HBr), and maleic acid (MA)) were obtained and characterized using single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and thermogravimetry (TG). The solubility and dissolution rate of all salts were systematically studied in water and phosphate buffer (pH 6.86) solutions. The accelerated stability tests indicated that all salts, except SAF-MA, had good stability under high humidity conditions.