High Performance Liquid Chromatographic Estimation of Drotaverine Hydrochloride and Mefenamic Acid in Human Plasma

The present work describes a reverse phase HPLC method for the quantitation of drotaverine hydrochloride and mefenamic acid in human plasma. Organic solvent system used for liquid extraction composed of dichloromethane, and isopropyl alcohol in the ratio 80:20 (v/v). The compounds were separated on a Thermo BDS Hypersil C₈ (25.0 cm×4.6 mm, 5 µm particle size) column in isocratic mode with a mixture of acetonitrile and ammonium acetate buffer (20 mM, pH 3.5 ± 0.05 adjusted with 85% phosphoric acid) in a ratio of 55: 45 (v/v), as the mobile phase, at a flow rate of 1.0 mL min^-1. The effluent was monitored by UV detection at 230 nm. The method was validated for accuracy, precision, specificity, linearity, and sensitivity. The total chromatographic analysis time was approximately 10 min with diclofenac sodium (internal standard), drotaverine hydrochloride and mefenamic acid, eluting with retention times of 6.89, 8.21 and 9.67 min, respectively. Calibration plots were linear within the range of 32-960 ng mL^-1 and 100-3000 ng mL^-1 for drotaverine hydrochloride and mefenamic acid, respectively. The limit of detection values were 11 and 33 ng mL^-1 and the limit of quantitation values were 32 and 100 ng mL^-1 for drotaverine hydrochloride and mefenamic acid, respectively. Results from analysis of quality control samples at concentrations of 90, 450 and 750 ng mL^-1 for drotaverine hydrochloride and 300, 1600 and 2400 ng mL^-1 for mefenamic acid, were indicative of good repeatability and precision. Recovery from plasma was 98.68% for drotaverine hydrochloride and 94.51% for mefenamic acid.