Novel Freely Soluble Minoxidil Salt: The Potential of Citric Acid and Tartaric Acid in Solubilization

Abstract

Androgenic alopecia is a common hair loss that affects both males and females, causes a decrease in hair follicles and may result in terminal hair loss. Minoxidil (MNX) is a heterocyclic drug with multiple hydrogen-bonding sites which is widely used for hair growth promotion. This drug has low water solubility and belongs to class II of the Biopharmaceutics Classification System (BCS).An attempt was made to generate solid forms of MNX with two carboxylic acids. Two multi-component assemblies; a crystalline salt and an amorphous salt between MNX and two carboxylic acids (TA and CA) were obtained and characterized by XPRD, DSC, and FTIR.Based on their diffraction pattern and intensity, TA salt of MNX was crystalline while the CA salt was amorphous. Compared to the crystalline MNX, the amorphous compounds show significant improvement in drug solubility. Given the effect of intermolecular interaction, it can be speculated that the hydrogen bonding is responsible for the improved solubility. In conclusion, CA shows to be a promising coformer for co-amorphous MNX. The striking effect of CA on MNX solubility makes it a great candidate for the development of a highly soluble MNX drug delivery system.