Stability Indicating HPLC Method for Simultaneous Determination of Thiocolchicoside and Lornoxicam

A simple, specific, accurate and stability-indicating reversed phase high performance liquid chromatographic method was developed for the simultaneous determination of thiocolchicoside  and lornoxicam, using a RP-18 column and a mobile phase composed of 10mM ammonium acetate : methanol(50:50), pH7 adjusted with 1%triethyl amine. The retention time of thiocolchicoside and lornoxicam were found to be 4.6 and 10.2 min, respectively. Linearity was established for both thiocolchicoside and lornoxicam in the range of 1-10 µg/ml. The percentage recoveries of thiocolchicoside and lornoxicam were found to be 100.45±0.4489 and 100.70±0.5111, respectively. Both the drugs were subjected to acid, alkali and neutral hydrolysis, oxidation, dry heat, and photolytic degradation. The degradation studies indicated thiocolchicoside to be susceptible to acid, alkaline and neutral hydrolysis while lornoxicam showed degradation under acid and alkali. The degradation products of thiocolchicoside and lornoxicam were well resolved from the pure drugs with significant differences in the retention time values. This method can be successfully employed for simultaneous quantitative analysis of thiocolchicoside and lornoxicam in bulk drugs and formulations.