A new spectrophotometric method based on the oxidation reaction between iodide and iodate in the presence of the carboxylic acid form of losartan potassium (LP) has been developed for the estimation of LP in pharmaceutical products . The HPLC/MS method, kinetic studies, and core composite design method were used for the formation reactions, equilibration, and determination of stability duration and experimental conditions, respectively. The developed spectrophotometric method was validated. The equilibration period was calculated as 10 minutes. 0.05 M KI and 0.003 M KIO3, and the amount was calculated as 1.953 mL (0.0195 M) and 1.961 mL (0.00117 M), respectively; and the temperature was measured as 32.3 °C. The method was revealed to be linear between 4-30 μg/mL with a correlation coefficient of 0.9996. The LOD and LOQ parameters were calculated as 0.61 and 1.85 μg/mL, respectively. The pharmaceutical preparations were analyzed using the developed kinetic spectrophotometric method. The results obtained ranged between 94.9% and 100.9%.Keywords: losartan potassium, central composite design, spectrophotometric methodHypertension, a major and independent risk factor for cardiovascular disease, is best managed by maintaining blood pressure greater than 140/90 mmHg[1].Including angiotensin II receptors, many of the receptor antagonists are the receptors that control blood pressure[2]. The new member of the antihypertensive agents called as angiotensin II receptor antagonists do not present significant side effects[3]. Losartan potassium (LP) is the first angiotensin II receptor antagonist and chemically is used as an antihypertensive agent that specifically blocks the angiotensin II type 1 receptor[4]. Simple and rapid analytical methods must be developed... half of the article... reported in the literature[26]. LP was also one of the drugs of the sartan group including the mentioned functional group. But the oxidation reaction between IO3 and LP has not yet been studied. Therefore, the aim of this work was to develop, optimize and validate a new specific, accurate, precise and sensitive spectrophotometric method based on the oxidation reaction between iodide and iodate in the presence of carboxylic acid form of LP which produces a color product yellow (λmax=286 nm) to determine LP in pharmaceutical tablets. The optimization of the reaction conditions was performed by applying a response surface methodology based on the central composite design which can save time and effort by estimating the optimal conditions. Furthermore, the kinetic study of the reaction was performed to avoid the interference of the colored and/or turbid background of the samples.