Effect of cogrinding time on the release of pentoxifylline from waxy matrix tablets

The release of pentoxifylline from matrix tablets containing palmitic or behenic acids, as waxes, and prepared via cogrinding was investigated. X-ray powder diffraction analysis of the ground drug-wax indicated that particle size could be reduced by grinding without polymorphic transformation. After the coground mixed powder was compressed at 1000 kg/cm2, the drug-release rate from the tablet was evaluated in pH 6.8 buffer at 37 degrees C. The drug-release profiles could be fitted to the Cobby model. The release rate decreased with an increased grinding time and increased significantly with an increased proportion of the drug. The drug-release rate constant from the matrix was calculated using the Cobby equation and the drug-release profiles. Scanning electron microphotographs of the coground product after dissolution tests suggested that mechanochemical energy had been used to cover the drug particles.