298DEVELOPMENT AND VALIDATION OF QUALITY BY DESIGN OPTIMIZED REVERSED PHASE HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF TELMISARTAN AND AMLODIPINEA simple, accurate, precise and robust method for simultaneous determination of amlodipine besylate (Aml) and telmisartan (Tel) in synthetic mixture has been developed. The method is RP-HPLC the separation was performed on a 5μm Prontosil C18column (150 × 4.6mm) using mobile phase consists of Methanol: potassium dihydrogen ortho phosphate buffer; pH 4.0 in the ratio of 75:25 (v/v). The flow rate was 0.7 ml/min and detection was carried out at wavelength 240 nm using PDA. The retention times of amlodipine besylate and telmisartan were 3.5 and 8.2 min, respectively. The method was linear over the concentration range of 2-16μg/ml for amlodipine and 1-35 μg/ml for telmisartan. The recoveries of amlodipine were found to be 99.96 %, 99.18%, 98.34% and for telmisartan 101.32%, 100.5%, 100.3% for the ratios 1:4,1:8,1:16 respectively. The validation of the method was carried out utilizing ICH guidelines. The described HPLC method was successfully employed for the analysis of each drug in their combined dosage form.ayabadran_87@windowslive.comResearch4102013Amlodipine,RP-HPLC,Simultaneous estimation,Telmisartan,Quality by DesignHamed M.EL-Fatatry,Ahmed Habib,Sherin F.Hammad,Aya I. BadranDepartment of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta University, Tanta, Egypt,Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta University, Tanta, Egypt,Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta University, Tanta, Egypt,Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Tanta University, Tanta, Egypt