Perphenazine-fumaric acid salts with improved solubility: preparation, physico-chemical characterization and in vitro dissolution

New compounds of perphenazine and fumaric acid in 2:1 and 1:2 molar ratios have been prepared by solvent evaporation with the aim of increasing the drug solubility. Their physico-chemical properties were thoroughly characterized by differential scanning calorimetry, powder X-ray diffraction, Fourier infrared spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. In addition, the crystal structure of the 2:1 salt was determined by single-crystal X-ray diffraction. The pharmaceutical characterization included solubility and dissolution studies in comparison with the commercial product Trilafon (R). Perphenazine solubility is strongly pH-dependent: the binary systems show improved solubility and intrinsic dissolution rate compared with perphenazine, but only the capsule formulation containing the 1 : 2 dihydrate sample shows a quick and complete dissolution behaviour at neutral pH. This sample could represent an interesting perphenazine formulation to improve drug bioavailability and perhaps reduce in vivo variability even when the gastric fluid pH is increased by the presence of food.