RP-HPLC Estimation of Tizanidine HCl and Valdecoxib in Combined Dosage Forms.

A reverse phase high performance liquid chromatography method was developed for simultaneous estimation of tizanidine HCl and valdecoxib in tablet formulation. The separation was achieved by Luna C₁₈ column and acetonitrile: phosphate buffer pH 3.5 (50:50 v/v) as eluent, at a flow rate of 0.5 ml/min. Detection was carried out at 227 nm. Etoricoxib was used as an internal standard. The retention time of tizanidine and valdecoxib was found to be 4.43 and 16.60 min, respectively. The method was validated for linearity, accuracy and precision. Linearity for tizanidine and valdecoxib were in the range 0.4-2.0 µg/ml and 4-20 µg/ml, respectively. The developed method was found to be accurate, precise and selective for simultaneous estimation of tizanidine and valdecoxib in tablets. [ABSTRACT FROM AUTHOR]