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A stability indicating LC method for olmesartan medoxomil

Ravi Kiran Kaja, K.V.Surendranath, P.V.V.Satyanarayana

A new, sensitive, stability indicating liquid chromatographic method has been developed for the separation, quantitative determination ofOlmesartan medoxomil fromits three impurities namely imp-1, imp-2, imp-3 and fromits degradation products in bulk drug, pharmaceutical dosage form used for the treatment of hypertension in the United States, Japan and European Countries. The developed method is also applicable for the related substances determination. Efficient chromatographic separation was achieved using a C18-CN column (1504.6) mm with 3.5 m particles with simple mobile phase combination of buffer and acetonitrile in the ratio of 65:35 (v/ v). Buffer consist of 20mM (2.76g in 1000 mL water) sodium dihydrogen ortho phosphate monohydrate, pH adjusted to 3.0 using phosphoric acid, delivered in isocratic mode at a flow rate of 1.0 mL min-1and quantitation was carried out using ultraviolet detection at a wavelength of 210 nm. In the developedHPLCmethod the resolution (RS)betweenOlmesartanmedoxomil and its impurities namely imp-1, imp-2 and imp-3 was found to be greater than 2.0. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in alkalinemedium, acid mediumand oxidative stress conditions. Olmesartanmedoxomilwas completely degraded to imp-1 in themild alkaline conditions. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.5%. The developed reverse phase LCmethod was validated with respect to linearity, accuracy, precision and robustness.