OXAZEPAM DISSOLUTION RATE FROM HYDROXYPROPYLMETHYLCELLULOSE MATRICES

The effect of some formulation variables on the release rate of oxazep am from hydroxypropylmethylcellulose (HPMC) has been investigated. The principal factors affecting this parameter were the content and molec ular weight of HPMC, and the drug particle size. pH modified the oxaze pam solubility; however, the liberation mechanism was not affected. Th e oxazepam release mechanism from these matrices has been examined. Va lues of the diffusional exponent n were in the range 0.61-0.74, indica ting that the release of drug was controlled by both diffusion and ero sion. When the tablets contained 30% HPMC K100 and the oxazepam partic le size was 0.210-0.250 mm, near-zero-order kinetics was obtained (n = 0.85), indicating that erosion plays an important role in the oxazepa m liberation.