Spectrophotometric Simultaneous Determination of Drotaverine Hydrochloride and Diclofenac Potassium in Combined Tablet Dosage Form by Ratio Derivative and Area Under Curve Method

Two simple, economical, precise and accurate methods for simultaneous determination of Drotaverine Hydrochloride (DRO) and Diclofenac Potassium (DIC) in combined tablet dosage form has been developed. The first method is based on Ratio Spectra Derivative and second method is Area Under Curve (AUC) Spectrophotometry. The amplitudes at 251.96 nm and 258.46 nm in the first derivative ratio spectra were selected to determine DRO and DIC, respectively and wavelength ranges of 237.4-247.2 nm and 271.1-282.8 nm were selected to determine DRO and DIC by AUC method, respectively in combined formulation. Beer’s law is obeyed in the concentration range of 8-40 μg mL^-1 for DRO and 5-25 μg mL^-1 for DIC for both the methods. The % assay for commercial formulation was found to be in the range 99.01 – 100.89% for DRO and 98.91 – 101.72% for DIC by the proposed methods. ICH guidelines were followed and methods were validated with respect to linearity, precision and accuracy. Recovery by both the methods was found in the range of 99.72 - 101.34% for DRO and 99.06 - 100.45% for DIC.