Preparation and In-vitro Characterization of Tizanidine Controlled-Release Microcapsular Matrices

Oral microencapsulated controlled release preparations of tizanidine hydrochloride (TIZ) were prepared by modified solvent evaporation technique using different proportions of ethyl cellulose as the retardant material. The microcapsules (TIZ1, TIZ2 and TIZ3) were compressed in to tablets (T-TIZ1, T-TIZ2 and T-TIZ3) for oral delivery. The prepared microcapsules were white, free flowing and spherical in shape, with the particle size varying from 215.38 ± 11.52 to 227.36 ± 12.89 μm and shows good drug entrapment efficiency. The 60% of TI2 release from microcapsules were found to be 2.15 ± 0.6, 2.98 ± 0.6 and 4.55 ± 0.8 h respectively for formulation TIZ1, TIZ2 and TIZ3 while their tablets i.e., T-TIZ1, T-TIZ2 and T-TIZ3 releases in 7.49 ± 1.2, 8.69 ± 0.6 and 15.24 ± 0.3 h respectively indicating more extension of time in tablet than microcapsules. The mechanism of drug release from tizanidine hydrochloride microcapsules and their tablets were studied by using Higuchi and Korsmeyer-Peppas models. The r-value for TIZ1, TIZ2 and TIZ3 indicates diffusion controlled with first order kinetic. The value of exponent coefficient (n) for T-TIZ1, T-TIZ2 and T-TIZ3 were found to be 0.874, 0.902 and 0.913 indicating anamolous, case-Ⅱ and case-Ⅱ transport release mechanism respectively.