Three Multivariate Calibration Methods for Simultaneous Spectrophotometric Determination of Olmesartan Medoxamil, Amlodipine Besylate and Hydrochlorothiazide in Their Combined Dosage Form

Olmesartan medoxamil (OLM, an angiotensin II receptor blocker), amlodipine besylate (AML, a dihydropyridine calcium channel blocker) and hydrochlorothiazide (HCT, a diuretic of the class of benzothiadiazines) 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, three multivariate calibration methods were applied for simultaneous spectrophotometric determination of OLM, AML and HCT in their combined pharmaceutical tablets The multivariate methods are classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS). The results showed the superiority of PLS over CLS and PCR for the analysis of the ternary mixture. The optimum assay conditions were established and the proposed methods were successfully applied for the assay of the three drugs in an independent validation set and combined pharmaceutical tablets with excellent recoveries. No interference was observed from common pharmaceutical additives. The results were favorably compared with those obtained by a reference spectrophotometric method.