Polymorphism and Crystal Growth of Phenylbutazone in Semisolid Preparations. Part One: Characterisation of Isolated Crystals from Commercial Creams of Phenylbutazone

Abstract

It has been observed that a commercial product of phenylbutazone cream (o/w type) shows gritty appearance. Large Crystals up to 1000 μm in diameter have been isolated from unexpired batches. New batches from the same product show crystal size up to 150 μm in diameter. Investigation of the physical characters of the isolated crystals have been done in comparison with a pure phenylbutazone sample (99.5%). UV-Spectrophotometric analysis of the isolated crystals indicates phenylbutazone content of 90%. However, TLC examination and UV, IR and NMR Spectra examinations indicate the absence of decomposition products. Oily material has been separated from the isolated crystals by phosphate buffer solution (pH. 6.90).

DSC examinations of the isolated crystals show two endothermic peaks at 76°C and 100.1°C and one exothermic peak at 81°C. The endothermic peak at 76°C is interpreted as a result of the interaction between phenylbutazone and the oily material.

The examination of the isolated crystals before and after isothermal transformation and during melting by both hot stage microscope, ESM, (IR) and DSC indicates that the presence of phenylbutazone in the crystals is not a mechanical entrapment. It suggests that phenylbutazone interacts with the fatty base on the molecular level and both crystallise out from the cream.