Development and Validation of Stability-Indicating RP-UPLC Method for Simultaneous Determination of Related Substances of S(？)Amlodipine and S(？)Metoprolol Succinate in Fixed Dose Combination Tablet Dosage Form

A novel, rapid, accurate, sensitive, precise, and stability-indicating reverse-phase ultra-performance liquid chromatographic (RP-UPLC) method was developed and validated for determination of related substances of S(？)Amlodipine and S(？)Metoprolol Succinate in fixed dose combination tablet dosage form. The chromatographic separation was achieved with the use of Acquity UPLC HSS T3, 1.8？μm, 2.1 × 100？mm analytical column at 45°C employing a gradient elution. Mobile phase consisting of mobile phase-A (solution containing 5.0？gm of sodium dihydrogen phosphate monohydrate per liter of water and Acetonitrile in the ratio of 95？:？5) and mobile phase-B (Acetonitrile) was used at a flow rate of 0.5？mL？min？1 with injection volume of 10？μL and the detection was done at 232？nm using UV detector. The retention times of S(？)Metoprolol Succinate and S(？)Amlodipine were found to be 2.8 minutes and 8.1 minutes, respectively. During method validation all the parameters were evaluated as per ICH guidelines, which remained well within acceptable limits. This method can be used for the estimation of related substances of S(？)Amlodipine and S(？)Metoprolol Succinate in fixed dose combination tablet dosage form. 1. Introduction The combination of calcium channel blocker, that is, S(？)Amlodipine Besilate (Figure 1), and β1-adrenoceptor blocker, that is, S(？)Metoprolol Succinate (Figure 2), is more effective for the treatment of exercise-induced angina pectoris than β-adrenoceptor blocker immunotherapy. S(？)Amlodipine Besilate is a long-acting calcium channel blocker (dihydropyridine DHP class) used as an antihypertensive and in the treatment of anginal chest pain. S(？)Metoprolol Succinate is a selective β1 receptor blocker used in treatment of several diseases of the cardiovascular system, especially hypertension. The formulation is available as bilayer tablets containing S(？)Amlodipine Besilate as immediate release and S(？)Metoprolol Succinate as extended release. Figure 1: Chemical structure of S(？)Amlodipine Besilate. Figure 2: Chemical structure of S(？)Metoprolol Succinate. From the literature review, we found that there are some spectrophotometric methods available for simultaneous estimation of Amlodipine and Metoprolol in tablet dosage form [1, 2] and few high performance liquid chromatographic analytical methods are published for determination of Amlodipine Besilate and Metoprolol Succinate in combination of pharmaceutical formulations [3–7]; some analytical methods are also available for estimation of Amlodipine and Metoprolol in tablets having Amlodipine as immediate