Formulation and Evaluation of Gastro Retentive Drug Delivery System of Tizanidine Hydrochloride: A Review
Gastro Retentive Sustained Drug Delivery System is a useful approach to avoid impredictable Gastric Empting Time (GET). The incorporation of drug in sustained release Gastro Retentive Dosage forms remains in the stomach for prolonged period of time. Thus, improves the gastric residence time which ultimately increases bioavailability of the drug. Several approaches are used for prolongation of gastric residence time which includes floating drug delivery systems, swelling and expanding systems, bioadhesive systems, modified shape systems, single and multiple unit gas generating systems, high density systems etc. The present interest is to develop floating matrix tablets of Tizanidine HCl (imidazoline derivative) by using Effervescent gas generating systems by incorporating Sodium bicarbonate as gas generating agent. The effect of Citric acid is determined on drug release profile and floating properties. Various viscosity grade polymers like HPMC (K4m&K400m) and Psyllium Husk are used which plays a major role in controlling invitro drug release of the formulation. Different formulations are prepared with different compositions using wet granulation method and evaluated for various physico chemical properties like hardness, thickness, friability drug content, weight variation, floating lag time and floating time of the drug. Based on the invitro drug release, final optimised formula is selected which releases 75% of the drug in 12 hours and remains floating in the gastric fluid for extended period of time. Thus, reduces frequency of dosing.