RP-HPLC estimation of rofecoxib and tizanidine in combination tablets

A reverse phase high performance liquid chromatography method was developed for the simultaneous estimation of rofecoxib and tizanidine in tablet formulations. The separation was achieved by Luna C₁₈ column and methanol : phosphate buffer pH 3.5 (55:45 v/v) as eluent, at a flow rate of 1 ml/min. Detection was carried out at 240 nm. Valdecoxib was used as an internal standard. The retention time of rofecoxib and tizanidine was found to be 4.53 and 5.92 min, respectively. The method has been validated for linearity accuracy and precision. Linearity for tizanidine and rofecoxib were in the range of 0.6-1.4 μg/ml and 7.5-17.5 μg/ml, respectively. The mean recoveries obtained for tizanidine and rofecoxib were 98.73% and 99.70%, respectively. The developed method was found to be accurate, precise, selective and rapid for simultaneous estimation of rofecoxib and tizanidine in tablets.