Formulation and Evaluation of Floating Microspheres of Tizanidine Hydrochloride

Microspheres are free flowing powders having particle size in the range of 1-1000µm with biologically active drugs intended for providing constant and prolonged therapeutical effect. Tizanidine Hydrochloride is a skeletal muscle relaxant, is a BCS class II drug with low bioavailability (40%) and short half-life (2.5 hours). It is better absorbed from the stomach, making it a suitable candidate for gastro-retentive formulations. To enhance its retention in the stomach and reduce dosing frequency, this study aimed to create optimized floating microspheres using ionotropic gelation techniques. The microspheres were developed using HPMC K4M and Eudragit RS100 as polymeric agents for controlling release. The formulation process was guided by Design Expert software (version 13, Stat-Ease). Comprehensive evaluations were conducted, including flow properties, buoyancy, release behaviour and drug entrapment. The best performing batch, F2 showed 99.3% release over 12 hours and good floating ability. Polymer concentration was positively correlated with both particle-size and buoyancy, with Eudragit RS100 having slightly greater buoyancy-enhancing effect than HPMC K4M. A balance between both the polymers produced an optimal buoyancy. Drug content and entrapment efficiency improved with higher polymers levels. The %drug release was the highest for the preparation with highest concentration of the polymers. The findings confirm that an appropriate blend of the chosen polymers enables successful formulation of gastro-retentive controlled-release microspheres of Tizanidine hydrochloride.