Determination of angiotensin II receptor antagonist (E4177) in human plasma and urine by high-performance liquid chromatography

A sensitive reversed-phase high-performance liquid chromatographic (HPLC) method with fluorescence detection was developed for the analysis of a new angiotensin II receptor antagonist, E4177, in human plasma and urine. The analyte and internal standard (I.S.) are extracted from acidified plasma and urine by liquid-liquid extraction and then refined by solid-phase extraction. The extraction recovery was greater than 90%. E4177 and I.S. were separated from endogenous components in plasma and urine on a C18 column using a mobile phase of acetonitrile-water-85% phosphoric acid (27.3:72.0:0.7, v/v). The eluent was monitored by fluorescence with excitation and emission set at 280 and 380 nm, respectively. The assay was linear from 2.5 to 1000 ng/ml of plasma and from 5 to 1500 ng/ml of urine. The limit of quantification was 2.5 and 5 ng/ml for plasma and urine, respectively. Inter- and intra-day coefficients of variation for the plasma and urine ranged from 0.6 to 4.7%. E4177 was stable in plasma and urine for at least 9 months during storage at -20 degrees C, respectively. The method was successfully applied to the determination of E4177 in plasma and urine for a pharmacokinetic study.