A reverse phase-high performance Liquid chromatography method is a simple, accurate, precise and reproducible one. UV-Spectrophotometric simultaneous equation method is adopted by official compendia for the stable substance that have reasonably broad absorption bands and which are practically unaffected by the variations of Instrumental parameters. The use of standard A(1%1cm) value avoids the need to prepare a standard solution of the reference substance in order to determine absorptivity. A reverse phase high performance liquid chromatography method has been developed for the simultaneous estimation of Olmesartan medoxomil and Hydrochlorthiazide acid in tablet dosage form using C18 column (LC 20 AT Isocratic) in Isocratic mode. The mobile phase consisted of Acetonitrile, methanol and 20 μl phosphate buffer adjusted to PH 3.5 in ratio of 60:20:20 v/v with ultraviolet visible detection at 230 nm. The method was linear over the concentration range for Olmesartan medoxomil 5 - 70μg/ml and for Hydrochlorthiazide 5 – 50μg/ml. The mean recovery was found to be in the range of 98% to 102%. The Validation method was carried out using International Conference on Hormonisation Guidelines. The described RP-HPLC method was successfully employed for the analysis of Pharmaceutical formulations containing combined dosage form.
