Nitrofurantoin-p-Aminobenzoic Acid Cocrystal: Hydration Stability and Dissolution Rate Studies

Nitrofurantoin (NF) drug is known to transform to a hydrate form in aqueous medium. The hydration stability and dissolution rate of a few cocrystals of NF were compared with that of its stable beta polymorph and hydrate form II. Hydrogen bonding and molecular packing in the novel cocrystal structures were analyzed. Pharmaceutical cocrystals of NF with p-aminobenzoic acid (PABA) and urea showed superior physicochemical properties compared with the known L-arginine salt hydrate. All the solid-state adducts were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, differential scanning calorimetry, and thermogravimetric analysis. NF-PABA cocrystal was found to be superior among the compounds studied in terms of minimal transformation to NF hydrate and comparable dissolution rate to the reference drug. (C) 2011 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:3233-3244, 2011