Formulation and Evaluation of Sustained Release Tablets of Chlorzoxazone

Chlorzoxazone is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain and discomfort which are having shorter half life (1.1hour) with the dose administration of 3-4 times a day. The aim of the study was to prepare and evaluate the Chlorzoxazone sustained release tablets in order to reduce the dose frequency and to improve the patient compliance. The tablets were prepared by direct compression method using synthetic polymers such as HPMC K15M (F1, F2 and F3), HPMC K100M (F4, F5 and F6) individually at different concentrations (45, 60, 75mg) and their combinations at 1:2 (F7) and 1:1 (F8) ratios. The tablets were evaluated for weight variation, hardness, friability, thickness, drug content uniformity and in-vitro drug release. All the formulations have passed in physical characterization as per the standard limits and found to be 147.7±1.2 mg in average weight, hardness ranges from 3.8±0.04 kg/cm to 5.03±0.15 kg/cm, 1.99±0.05mm in thickness with the friability ranges from 0.2±0.01% to 0.5±0.04% and 90.06±0.9% to 105.1±0.5% in drug content. FT-IR studies, reveals that the drug was compatible with excipients. Based on the in-vitro drug release F3, F6 and F8 showed sustained release effect up to 8 hours (99.8%, 99% and 101%) having higher concentration high viscous polymer HPMC K100M. The t50% and t90% for F3 was 3.5 and 7.5 hours whereas for F6, F8 it was 4.0 and 7.5hours. The drug release pattern was followed by korsmeyer’s-peppas model for F3 (0.9726), F6 (0.9952) and F8 (0.9856) respectively which depicts the diffusion mechanism.