Int. J. Pharm. Sci. Rev. Res., 20(1), M ay – Jun 2013; nᵒ 03, 11-15 ISSN 0976 – 044X International Journal of Pharmaceutical Sciences Review and Research Available online at www.globalresearchonline.net 11 Lily P. Peikova 1 * , Boyka G. Tsvetkova 1 , Bistra. D. Kostova 2 , Dimitar R. Rachev 2 1 Medical University – Sofia, Faculty of Pharmacy, 1 Department of Pharmaceutical chemistry, Medical University of Sofia, Faculty of Pharmacy, 2 Dunav str., 1000 Sofia, Bulgaria. 2 Department of Pharmaceutical Technology and Biopharmaceutics, Medical University of Sofia, Faculty of Pharmacy, 2 Dunav str., 1000 Sofia, Bulgaria. Accepted on: 03-03-2013; Finalized on: 30-04-2013. ABSTRACT This paper describes the development and validation of a high-performance liquid chromatographic analytical procedure for simultaneous determination of Amlodipine Besylate (AML) and Lisinopril (LIZ) in model tablet formulations. The separation was achieved with a C 18 (250 mm x 4.6 mm, 10 μm) column, at room temperature in an isocratic mode, with the mobile phase containing acetonitrile and 0.5 M sodium acetate buffer (25:75). The flow rate was 1.5 ml/min and the eluent was monitored at 215 nm. The selected chromatographic conditions were found to effectively separate Amlodipine Besylate and Lisinopril, with retention times of 6.67 min and 12.00 min, respectively. The method was validated for specificity, linearity, precision, accuracy, LOD and LOQ. The calibration curves were linear in the concentration range of 5.00-40.00 μg/ ml for both AML and LIZ. The intra- and inter-day relative standard deviations for both the components were <2.0 %. The analytical procedure was applied in identification, purity and assay tests on model drug formulations. It was established that the developed analytical procedure was successfully used for routine analysis of AML and LIZ in model drug dosage forms without any interference from included excipients. Keywords: Amlodipine Besylate, Lisinopril, liquid chromatography, validation, model tablet formulations. INTRODUCTION he goal of antihypertensive therapy is to abolish the risks associated with blood pressure elevation without adversely affecting quality of life. Drug selection is based on efficacy in lowering blood pressure and in reducing cardiovascular end points including stroke, myocardial infarction and heart failure. There has been a marked increase in the use of combinations of antihypertensive drugs with complementary mechanisms of action, with the aim of reducing blood pressure levels more rapidly and improving treatment compliance. Amlodipine Besylate, 2-[(2-aminoethoxy)methyl]-4-(2- chlorophenyl)-3-ethoxycarbonyl-5-methoxycarbonyl-6- methyl-1,4 dihydropyridine benzene sulphonate, is a dihydropyridine calcium-channel blocker that inhibits the transmembrane influx of calcium ions into vascular smooth muscles and cardiac muscles, which in turn affects their contractile process and results in reduced blood pressure. It is used in the treatment of hypertension and coronary artery diseases 1, 2 . Lisinopril is a drug of the angiotensin converting enzyme (ACE) inhibitor class primarily used in treatment of hypertension, congestive heart failure, and heart attacks and also in preventing renal and retinal complications of diabetes 2 . Its indications, contraindications and side effects are as those for all ACE inhibitors. It is designated chemically as N2-[(1S )-1-carboxy-3-phenylpropyl]-L-lysyl- L-proline. Certain successful attempts have been made for the determination of AML 3-12 and LIZ 13-32 in pharmaceuticals using different analytical techniques including spectrophotometry, spectrofluorimetry, fluorimetry, liquid chromatography, thin-layer chromatography, titrimetry, voltammetry, alone or in combination with other drugs. Some analytical methods for simultaneous estimation of both drugs have been recently reported 33-41 . The present study emphasizes on the determination of Amlodipine Besylate and Lisinopril in model drug tablets by using high performance liquid chromatography. M ATERIALS AND M ETHODS M aterials Amlodipine besyalte and lisinopril were used as standards. HPLC grade acetonitrile was used to prepare the mobile phase. All other chemicals used for the chromatographic experiments were of a reagent grade. For the preparation of the model tablet formulations, amlodipine and lisinopril substances of Eur.Ph. grade were used. Ludipress (BASF), microcrystalline cellulose (Avicel PH 102), croscarmellose (Ac-Di-Sol), Calcium phosphate dibasic anhydrous and magnesium stearate were used as excipients in the preparation of the tablets. All used excipients were of an analytical grade. M ethods Instrumentation and chromatographic conditions Chromatographic separation was performed on a modular HPLC system LC-10A Shimadzu (Japan) comprising a LC-10A pump, a solvent degasser DGU-3A, a Rheodyne injector with 20 µl loop, a column oven CTO- 10A, SPD-M10A UV detector with a fixed wavelength and Investigations and HPLC Assay of M odel Formulations Containing Amlodipine Besylate and Lisinopril T Research Article