Abstract
Olmesartan medoxamil (OLM, an angiotensin II receptor blocker) and amlodipine besylate (AML, a dihydropyridine calcium channel blocker), are co-formulated in a single-dose combination for the treatment of hypertensive patients whose blood pressure is not adequately controlled on either component monotherapy. In this work, two simple, sensitive, and reliable spectrofluorimetric methods have been developed and validated for the simultaneous determination of OLM and AML in their combined tablets. These methods are first derivative and ratio subtraction methods for OLM and AML, respectively. The optimum assay conditions were established and the methods were validated with respect to linearity, sensitivity, accuracy, precision and specificity. Regression analysis showed excellent correlation between the peak amplitude or fluorescence intensity with the concentration over the concentration ranges of 0.08-1 and 0.25-2 mu g mL(-1) for OLM and AML, respectively. The proposed methods were successfully applied for the assay of the two drugs in their laboratory prepared mixtures and combined pharmaceutical tablets with recoveries not less than 99.0%. No interference was observed from common pharmaceutical additives. The results were favourably compared with those obtained by a reference method.