539NOVEL RP-HPLC METHOD FOR SIMULTANEOUS DETERMINATION OF OLMESARTAN MEDOXOMIL, AMLODIPINE BESYLATE AND HYDROCHLOROTHIAZIDE IN TABLET DOSAGE FORMA convenient, rapid, simple, specific, accurate, precise, economical isocratic Reversed Phase-High Performance Liquid Chromatography (RP-HPLC) method was developed and validated for simultaneous estimation of new combination of Olmesartan medoxomil (OLM), Amlodipine besylate (AMD) and Hydrochlorothiazide (HCTZ) in its dosage form. RP-HPLC method was carried out by utilizing Welchrom C18 Column (4.6 X 250 mm, 5µm), Shimadzu LC-20AT Prominence Liquid Chromatograph. The mobile phase comprised of 10 mM Phosphate buffer (pH-3.0): Acetonitrile (50:50 v/v). The flow rate was adjusted to 1.0 mL/minute with the responses measured at 262 nm utilizing Shimadzu SPD-20A Prominence UV-Vis detector. The chromatogram showed a peak of 5.410 minutes for OLM, 4.067 minutes for AMD and 3.353 minutes for HCTZ. Good linearity was obtained in the range of 8-40 μg/ mL, 2-10 μg/ mL and 5-25 µg/mL for OLM, AMD and HCTZ respectively. The linear regression equations for OLM, AMD and HCTZ were y=27.61x + 0.58, y = 55.80x + 0.988 and y = 37.75x + 0.345 respectively.The limit of detection (LOD) for OLM, AMD and HCTZ were found to be 0.150 µg/mL, 0.0795 µg/mL and 0.1272 µg/mL respectively and the Limit of quantitation (LOQ) for OLM, AMD, HCTZ were found to be 0.456 µg/mL, 0.2410 µg/mL, 0.3856 µg/mL respectively. The proposed method has resulted high recovery values (99.74, 99.86 and 99.81 for OLM, AMD and HCTZ respectively). The assay content of OLM, AMD and HCTZ were determined and mean assay values were found to 99.564 %, 99.786 % and 99.567 % for OLM, AMD and HCTZ respectively in marketed tablets. Validation of the developed method was carried out for its accuracy, precision and ruggedness according to ICH Q2 (R1) guidelines. Thus the present study is an excellent method for the simultaneous separation and determination of all the three drugs in combined dosage form without any interference of excipientsbanuman35@gmail.comResearch5122014Olmesartan medoxomil,Amlodipine besylate,Hydrochlorothiazide,Isocratic RP-HPLCP. Ravisankar,J. Swathi,K.V.S. Santosh Kumar,P. Srinivasa BabuDepartment of Pharmaceutical Analysis and Quality Assurance, Vignan Pharmacy College, Vadlamudi, Guntur- 522 213. Andhra Pradesh, India.,Department of Pharmaceutical Analysis and Quality Assurance, Vignan Pharmacy College, Vadlamudi, Guntur- 522 213. Andhra Pradesh, India.,Department of Pharmaceutical Analysis and Quality Assurance, Vignan Pharmacy College, Vadlamudi, Guntur- 522 213. Andhra Pradesh, India.,Department of Pharmaceutical Analysis and Quality Assurance, Vignan Pharmacy College, Vadlamudi, Guntur- 522 213. Andhra Pradesh, India.