Solubility of carbamazepine, nicotinamide and carbamazepine-nicotinamide cocrystal in ethanol-water mixtures

Abstract

Solubility is an important physiochemical property of pharmaceutical compounds, and cocrystallization is one method used to improve the solubility of drugs. Carbamazepine is a drug from class II, according to the biopharmaceutical classification system, and it forms a cocrystal with nicotinamide. Carbamazepine cocrystallized with nicotinamide was synthesized using the solvent evaporation approach, and its characteristics were determined using differential scanning calorimetry and powder X-ray diffractometry. The solubility of various solid phases in ethanol + water mixtures was investigated at different temperatures using the shake-flask method, and the resulting precipitates were characterized. The solubility of carbamazepine was increased with the addition of ethanol up to a mass fraction of 0.8. Nevertheless, maximum solubility of NIC is observed in neat solvent (water). While the solubility of a cocrystal depends on the concentration of the coformer and its stability in the solution. (C) 2013 Elsevier B.V. All rights reserved.