Synchronized stability indicating RP-LC methods for determination of metolazone with losartan potassium or spironolactone in presence of their degradation products

Abstract

Two precise and selective stability-indicating RP-LC methods have been developed and validated for simultaneous determination of metolazone in its binary mixture with losartan potassium (method 1) and spironolactone (method 2) in the presence of their degradation products. For method 1, the chromatographic separation was achieved on Kromasil C18 column, the mobile phase consisted of a mixture of 0.1% ortho-phosphoric acid in acetonitrile and 0.1% ortho-phosphoric acid in water (28:72, v/v) pumped at flow rate 2 mL/min and UV detection at 235 nm. Linearity was determined over the concentration range of 2–16µg/mL for metolazone and 40–320µg/mL for losartan potassium. For method 2, chromatographic separation of metolazone and spironolactone was achieved on a Symmetry C8 column using a mobile phase that consisted of acetonitrile, methanol, and 0.1% ortho-phosphoric in water in gradient mode pumped at a flow rate 1.5 mL/min with programed wavelength detection. Linearity was determined over the concentration range of 2–16µg/mL for metolazone and 20–160µg/mL for spironolactone. The suggested methods were proved to be highly selective, precise and accurate for simultaneous determination of the cited drugs in their combined pharmaceutical dosage form in the presence of their degradation products. The proposed methods were validated in compliance with ICH guidelines.HighlightsSynchronized determination of metolazone and co-formulated drugs in presence of their degradation products.Act as a method for screening of metolazone and co-formulated drugs in quality control laboratories.Validation of suggested methods according to ICH guidelines.The pathway of degradation of metolazone under different stress conditions was proposed.