Chromatographic methods of identification and quantification of amlodipine in tablets «Ekvator» have been dveloped. The method of quantitative determination (amlodipine) meets the criteria of specificity, linearity, accuracy and precision (convergence) in the range of 50-150 % of the nominal content.
Key words: amlodipine, pharmacopoeial standard sample, HPLC, varification characteristics.
Introduction. Amlodipine (Norvasc (Pfizer) and generics) (as besylate, mesylate or maleate) is a medication used to lower blood pressure and prevent chest pain. It belongs to a group of medications known as long-acting dihydropyridine-type calcium channel blockers. Like other medications in this group, amlodipine lowers blood pressure by relaxing the muscles controlling the diameter of blood vessels in the body. Widening of these blood vessels lowers blood pressure. In angina, amlodipine increases blood flow to the heart muscle to relieve pain due to angina. It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. 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.
Experimental data suggest amlodipine binds to both dihydropyridine and nondihydropyridine binding sites. The contractile processes of cardiac muscle and vascular smooth muscle are dependent upon the movement of extracellular calcium ions into these cells through specific ion channels. Amlodipine is a peripheral arterial vasodilator that acts directly on vascular smooth muscle to cause a reduction in peripheral vascular resistance and reduction in blood pressure. Also, as a calcium channel blocker amlodipine is expected to inhibit the currents of L-type Cav1.3 channels in the zona glomerulosa of the adrenal cortex, reducing aldosterone production and corroborating to lower blood pressure . Pfizer's patent protection on Norvasc lasted until 2007; total patent expiration occurred later in 2007.
A number of generic versions are available. In the United Kingdom, tablets of amlodipine from different suppliers may contain different salts. The strength of the tablets is expressed in terms of amlodipine base, i.e., without the salts. Tablets containing different salts are therefore considered interchangeable.The efficacy and tolerability of a fixed-dose combination of amlodipine 5 mg and perindopril 4 mg, an angiotensin converting enzyme inhibitor, have recently been confirmed in a prospective, observational, multicentre trial of 1250 hypertensive patients. Therefore, the development of methods for identification and quantification of amlodipine in tablets is an important task of pharmaceutical chemistry and standardization of medicines.
The aim of our study was to develop chromatographic methods of identification and quantification of amlodipine in tablets «Ekvator».
Materials and methods of research. The objects of the study were tablets «Ekvator». The standard used Pharmacopoeial standard sample SPU of amlodipine.
Results and discussion. We did analysis amlodipine in tablets by HPLC. In the chromatogram obtained test solution in terms of quantitative determination must be observed at its peak, which is characteristic of amlodipine retention time that corresponds to the retention time in chromatography in standard solution of amlodipine. In developing HPLC methods, amlodipine identification of the medicinal product, we had conducted preliminary studies of the chromatographic behavior of these substances in various chromatographic conditions. Optimally, based on analytical and economic reasons, there was a mixture of acetonitrile R-methanol R-triethylamine R (retention time - 7 min) [2, 3]. According to the SPU for the developed method, it was necessary to varificate. We studied some varification characteristics: linearity, accuracy and precision (convergence), the range of application.
Conclusion. Considering the results obtained, our studies found out that this method of quantitative determination (amlodipine) meets the criteria of specificity, linearity, accuracy and precision (convergence) in the range of 50-150 % of the nominal content. These results fully meet the condition of validation characteristics «range of application» because the method of quantitative determination, as required by SPU must have the required linearity, accuracy and precision in the range of 80-120 % of the nominal content.