Development and Validation of Spectrophotometric Methods for Simultaneous Estimation of Indapamide and Amlodipine Besylate in Combined Dosage Form.

Two simple spectrophotometric methods have been developed for the simultaneous estimation of Indapamide and Amlodipine besylate in their combined dosage forms. In Dual wavelength Spectrophotometric method, two wavelengths on amlodipine besylate curve has been found out where it showed same absorbance at 256 nm and 360.0 nm. At 360.0 nm, Amlodipine besylate showed some absorbance while Indapamide showed zero absorbance. The method involved solving of an equation based on measurement of absorbances at two wavelengths 256 nm and 360.0 nm. In first order derivative spectrophotometric method in which, measurement of amplitudes at 237.4 nm (for IND) and 241 nm (for AML) in first derivative spectra. Developed methods were validated according to ICH guidelines. This methods obeyed Beer's law in the concentration range of 3–18 μg/ml for IND and 10–60 μg/ml for AML for dual wavelength Spectrophotometric method and 1.5–9 μg/ml for IND and 5–30 μg/ml for AML for first order derivative method.The proposed methods were found to be simple, accurate and reproducible for the routine analysis of both drugs in combined tablet dosage forms.