A stability indicating LC method was developed for simultaneous determination of amlodipine and valsartan in pharmaceutical dosage form. Efficient chromatographic separation was achieved on C8 stationary phase with simple combination of mobile phase-A (70？:？20？:？10？v/v/v of water？:？acetonitrile？:？methanol with 2？mL of Octylamine adjusted the pH to 2.50 + 0.05 with orthophosphoric acid) and mobile phase-B (Acetonitrile) delivered in gradient mode. Quantification was carried out using ultraviolet detection at 240？nm at flow rate of 1.0？mL/min with Injection Volume of 100？μL and ambient column temperature. This method was capable to detect both the drug components of Amlodipine and Valsartan in presence of their degradation products (Amlodipine Imp-A and Valsartan Impurity-B) with the detection level of 0.05%. Amlodipine/Valsartan and their combination drug product were exposed to thermal studies, photolytic, hydrolytic and oxidative stress conditions, and samples analysed. Peak homogeneity data of Amlodipine and Valsartan is obtained using PDA detector, demonstrating the specificity. The method shows excellent linearity over range of 0.05–2.0% for Amlodipine; Amlodipine Impurity-A and 0.05–1.0% for Valsartan and Valsartan Impurity-B. The correlation coefficient for Amlodipine and Valsartan are 0.9999. The proposed method was found to be suitable and accurate for quantitative determination and the stability study of Amlodipine and Valsartan in pharmaceutical preparations. 1. Introduction The amlodipine besylate component of amlodipine/valsartan tablets is chemically described as 3-ethyl-5-methyl (±)-2-[(2-aminoethoxy) methyl]-4-(2-chlorophenyl)-1, 4-dihydro-6-methyl-3, 5-pyridinedicarboxylate, monobenzenesulphonate [1]. Amlodipine is a dihydropyridine calcium antagonist (calcium ion antagonist or slow-channel blocker) that inhibits the movement of calcium ions into vascular smooth muscle cells and cardiac muscle cells. Amlodipine besylate has empirical formula of C20H25ClN2O5·C6H6O3S, and its molecular weight is 567.1, and its structural formula is shown in Scheme 1. Scheme 1: Amlodipine chemical structure. Valsartan is a nonpeptide, orally active and specific angiotensin II antagonist acting on the AT1 receptor subtype. valsartan is a white to practically white fine powder, soluble in ethanol and methanol and slightly soluble in water. Valsartan’s chemical name is N-(1-oxopentyl)-N-[[2′-(1？H-tetrazol-5-yl) [1, 1′-biphenyl]-4-yl] methyl]-L-valine [1]. Its empirical formula is C24H29N5O3, molecular weight is 435.5, and its structural formula is shown in
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