Mechanism of Hydration and Dehydration of Ciclopirox Ethanolamine (1:1)

Abstract

The antifungal agent ciclopirox ethanolamine (1:1), a stoichiometric compound between ethanolamine and 6-cyclohexyl-1-hydroxy-4-methylpyridin-2-(1H)-one, crystallizes as an anhydrate and a monohydrate. The structures of both phases have been characterized by single crystal X-ray diffraction and suggest that, at ambient temperature, ciclopirox ethanolamine (1:1) anhydrate and monohydrate should be classified as salts from the position of the protons in the Fourier difference map. The thermal dehydration process has been elucidated by thermal analyses (TGA/DSC), temperature resolved X-ray powder diffraction and Hot-Stage Microscopy. Moisture sorption and desorption investigations at room temperature under static and dynamic conditions (DVS) reveal that, if the dehydration is not implemented under a sufficient ethanolamine vapor pressure, the dehydration-hydration mechanism is not reversible. This behavior suggests that, at elevated temperature, ciclopirox ethanolamine (1:1) monohydrate could be contemplated...