Preparation and solid-state characterization of dapsone drug-drug co-crystals

Pharmaceutical co-crystals involving two active pharmaceutical ingredients are rarely revealed in the literature. In this work, crystal engineering principles were exercised to guide the design and synthesis of the Biopharmaceutics Classification System class IV drug dapsone (DAP). We reported six drug-drug co-crystals of DAP with sulfanilamide, flavone, luteolin, caffeine in 1:1 stoichiometry, caffeine in 1:2 stoichiometry, and 2(3H)-benzothiazolone. Bioactive coformers were deliberately selected. The resulting co-crystals were fully characterized by a range of analytical technologies, including X-ray powder diffraction, Fourier transform infrared spectroscopy, polarized light microscopy, differential scanning calorimetry, and thermogravimetric analysis, etc. Single-crystal structure analysis reveals that reoccurring supramolecular synthons are observed in different DAP co-crystals. Equilibrium solubility and intrinsic dissolution rates were also compared with those of the parent drug. This work expands the pharmaceutically acceptable solid forms of DAP and supplements the successful cases of drug-drug co-crystals. © 2014 American Chemical Society.