Multiple Crystal Forms of p-Aminosalicylic Acid: Salts, Salt Co-Crystal Hydrate, Co-Crystals, and Co-Crystal Polymorphs

Crystallization of p-aminosalicylic acid, an anti-tuberculosis drug, in the presence of pyridine derivatives as coformers led to formation of nine multicomponent solids that include salts, a salt co-crystal hydrate, co-crystals, and co-crystal polymorphs. Seven of them are new solid forms. The influence of the COOH center dot center dot center dot N-heterocycle synthon is examined in dictating the various crystal forms, the manifestation of which depends on solvent of crystallization and API-coformer composition in solution.