Simple and specific validated derivative spectrophotometric method for simultaneous quantification of drotaverine HCl andmefenamic acid combination in tablets

A simple and specific first-order-derivative spectorophotometric method has been developed and validated for simultaneous quantification of drotaverine HCl andmefenamic acid in combined tablet dosage formswithout any prior separation of components from the sample. Drotaverine HCl was determined at a wavelength of 253.8 nm (zero-crossing wavelength point ofmefenamic acid). Similarly,mefenamic acidwasmeasured at 304 nm (zero-crossing wavelength point of drotaverine hydrochloride) in phosphate buffer, pH 6.8 as solvent. The first derivative amplitude- concentration plotswere rectilinear over the range of 4-24 µg/mL for drotaverine HCl and mefenamic acid. Detection and quantitation limit were 0.4 and 1.21 µg/ mL for drotaverine HCl and 0.33 and 1.0 µg/mL for mefenamic acid, respectively. The%assay in commercial formulation was found to be in the range 99.00 – 100.00 for drotaverine HCl and 99.72 – 100.20 for mefenamic acid by the proposed method. The method was validated for precision and accuracy as per ICH guidelines. The proposed method can be effectively applied for routine analysis of drotaverine HCl and mefenamic acid in tablets.