Development and Validation of Stability Indicating RP-HPLC Method for the Determination of Metaxalone in Bulk and its Pharmaceutical Formulations

A stability indicating reverse phase HPLC method was developed for the determination of metaxalone, a skeletal muscle relaxant, present in bulk and its pharmaceutical formulations using gliclazide as the internal standard (I.S). A hypersil ODS C18 column (250 × 4.6 mm, packed with 5 micron) in an isocratic mode with mobile phase Acetonitrile: phosphate buffer 3.6 (50:50%v/v) was used at a flow rate of 0.8 mL/ min and effluent was monitored at 225 nm. The assay exhibited a linear dynamic range of 0.6-100 µg/mL. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The retention times were 5.13 min and 9.08 min for metaxalone and IS respectively. The extraction recovery of metaxalone from pharmaceutical dosage form (tablets) was >97% and the calibration curve was linear (r2 = 0.999) over the entire linear range. The method had an accuracy of >98% and LOD and LOQ of 0.2 µg/mL and 0.6 µg/mL respectively. The specificity of the proposed method was performed whereby metaxalone undergoes different stress conditions like oxidation, reduction, photolysis, acid and alkaline hydrolysis.