A rapid HPLC method for the determination of losartan in human plasma using a monolithic column.

A rapid and simple high-performance liquid chromatography (HPLC) method using a monolithic column has been developed for quantification of losartan (CAS 12450-98-8) in plasma. The assay enables the measurement of losartan for therapeutic drug monitoring. The method involves a simple, one-step extraction procedure. The analytical recovery was complete. The separation was carried out in reversed-phase conditions using a Chromolith Performance (RP-18e, 100 x 4.6 mm) column with an isocratic mobile phase consisting of 0.01 mol/L disodium hydrogen phosphate buffer-acetonitrile (60:40 v/v) adjusted to pH 3.5. The wavelength was set at 254 nm. Thioridazine (CAS 50-52-2) was used as internal standard. Losartan, thioridazine and the EXP 3174, the active metabolite of losartan, appeared 3.4, 5.0 and 10.5 min post injection, respectively. The calibration curve was linear over the concentration range 5-300 ng mL(-1) with a minimum detectable limit of 2 ng mL(-1). The coefficients of variation for the inter-day and intra-day assay were found to be less than 8 %. The applicability of this method for pharmacokinetic studies in humans was demonstrated. The present assay is rapid, simple, precise, and accurate and is suitable for pharmacokinetic studies.