Hydrochlorides, hydrates, hydronitrate, and an unanticipated hydrolysis product of famotidine

O (IV). The crystal structures reveal significant solid-state diversity: hemihydrate salt II exhibits two symmetry-independent famotidine hydrochloride molecules per asymmetric unit, while sesquihydrate salt IV shows four crystallographically-independent hydrochloride molecules and six symmetry-independent water molecules per standard unit. All four complexes display extensive hydrogen-bonded networks in the solid state. The detailed structural characterization of these crystalline complexes generates fundamental solid-state chemistry data; this knowledge is essential for predicting and controlling the drug performance and formulation stability of famotidine and crucially informs our development of PADs.