Ghulam Murtaza1 
,
Hanif Ullah1,
Shujaat Ali Khan1,
Sadullah Mir2,
Abida Kalsoom Khan2,
Bushra Nasir3,
Saira Azhar1,
Mubashir Ali Abid1
For correspondence:- Ghulam Murtaza Email: gmdogar356@gmail.com Tel:+92992383591
Received: 27 March 2014 Revised: 31 December 2014 Published: 28 February 2015
Citation: Murtaza G, Ullah H, Khan SA, Mir S, Khan AK, Nasir B, et al. Formulation and in vitro dissolution characteristics of sustained-release matrix tablets of tizanidine hydrochloride. Trop J Pharm Res 2015; 14(2):219-225 doi: 10.4314/tjpr.v14i2.5
© 2015 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..
Purpose: To formulate sustained-release (SR) matrix tablets of tizanidine hydrochloride (THC) and to investigate the effect of matrix polymer type on drug release profile of drug.
Methods: Matrix tablets of THC were prepared by direct compression method using a combination of hydroxypropylmethylcellulose (HPMC) and ethylcellulose (EC) in varying ratios. In all the formulations, the amount of THC was 6.87 mg (equivalent to 6 mg base). USP type-I (basket) apparatus was used for the dissolution study. The dissolution study was performed in 0.1M HCl for the first 2 h and in phosphate buffer (pH 6.8) for another 10 h. The dissolution data were subjected to drug release models to ascertain the kinetics of drug release. Additionally, in vitro swelling and buoyancy studies were carried out on the optimized formulation. The optimized formulation was compared with a commercial reference product using similarity factor (ƒ2) test.
Results: F4 formulation, containing 145 g of HPMC only, (with ƒ2 value of 67.38) was selected as optimized formulation (compared to the reference commercial product), and it released 97.84 % of the drug in 12 h. The release data showed best fit to first-order kinetics (R2 = 0.9963 - 0.9989), though non-significantly (p > 0.05) different from the Higuchi model (R2 = 0.9813 - 0.9955) except for formulation F6. Based on Koppcha model data, drug release mechanism involved both diffusion and erosion (n = 0.513 - 0.597) with diffusion being dominant. The optimized formulation exhibited 162 % swelling at the end of 11 h, after which no further weight gain occurred.
Conclusion: Suitable sustained-release tablets of tizanidine hydrochloride have been successfully prepared using direct compression Drug release is sustained by increasing the content of the matrix polymers used.
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