Abstract
Purpose : To formulate matrix type sustained-release (SR) tablets of tizanidine hydrochloride (TH) for prolonged drug release and improvement in motor activity after spinal injuries. Methods : Matrix tablets were prepared by the wet granulation method using four polymers (hydroxyl propyl methyl cellulose [HPMC] K 100, ethyl cellulose [EC], guar gum, and polyvinylpyrrolidone (PVP K30) and characterized for hardness, friability, drug content, swelling, weight variation, in vitro drug release, and in vivo motor function activity using the spinal injury rat model. Results : All tablets showed good drug content, hardness, and other physicochemical properties. The tablet formulations showed a percent drug release ranging from 92.54 ± 1.02 to 98.56 ± 1.26 % at the end of 12 h. Using the spinal injury rat model, negative control had a motor activity of only 12.75 %, while F4 (containing HPMC, EC, and PVP) and F5 (containing EC, guar gum, and PVP) had motor activities of 62.25% and 57.5%, respectively, compared with 68.0 % for normal controls. Conclusion : SR matrix tablets of TH showed significant improvement in motor activity in post-traumatic spinal injury rat model. Keywords : Sustained release tablet, Spinal injuries, Matrix tablet, Tizanidine hydrochloride
Highlights
Oral sustained-release (SR) drug delivery systems are designed to deliver therapeutically effective concentrations of drug to the systemic circulation over an extended period of time
Content uniformity for all formulations ranged from 94.72 ± 0.05 % to 98.80 ± 0.03 %, and the contents were in compliance with pharmacopoeia limits
The highest swelling was found for formulation F6, which contained HPMC and guar gum
Summary
Oral sustained-release (SR) drug delivery systems are designed to deliver therapeutically effective concentrations of drug to the systemic circulation over an extended period of time. Conventional dosage forms are associated with various limitations, such as drug plasma level fluctuations (leading to adverse effects or toxicity due to overdoses), high dosage frequency, high dosage requirements, and poor patient compliance. The drug plasma concentration must be maintained within a therapeutic range. The SR form decreases side effects and increases patient compliance, due to reduction in frequency of dosing. The SR form maintains constant blood levels, and avoids drug plasma level fluctuations associated with conventional immediate release formulations [1]. To repair the initial tissue damage, SI leads to complex cellular and molecular interactions within the central nervous system, and is characterized by the shearing of cell membranes and axons, disruption of the blood-spinal cord barrier, cell death, immune cell transmigration, and myelin degradation [2,3,4,5]
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