Characterization of Hydrochloride and Tannate Salts of Diphenhydramine

Proper characterization is an important aspect of any dosage form design. The objective of this work was to characterize tannate salt and hydrochloride salt of diphenhydramine. As a part of characterization studies, Differential scanning calorimetry was used to investigate thermal effects and nature of salts, supported by X-ray powder diffraction. Scanning electron microphotographs was used to surface topography of salts of diphenhydramine. Fourier-transform infrared spectroscopy, solubility study and flowability studies were carried out as part of characterization. Differential scanning calorimetry and X-ray powder diffraction studies indicated amorphous nature of the tannate while hydrochloride salt has crystalline properties. Scanning electron microphotographs indicated the differences in surface topography between both the salts. Solubility studies at different pH showed pH dependant solubility of both the salts and less solubility of tannate. Stability of bulk drug at accelerated conditions of 40( degrees )/75% RH was determined for both salts. Good stability of both salts was observed.