A new spectrofluorimetric method for determination of losartan potassium in rabbit plasma and its application to pharmacokinetic study

A new spectrofluorimetric method to determine losartan potassium (LP) in rabbit plasma is described. The method was based on measuring the native fluorescence of LP in acidic medium. Optimum excitation and emission wavelengths were found to be 248 nm and 410 nm, respectively, in methanol that was diluted with a sulfurous acid solution LP was extracted from rabbit plasma by methyl-tertiary-butyl-ether in acidic media and then back extracted with NaOH. The calibration curves were linear between 0.025 and 0.5 mu g/mL with a lower limit of detection 0.004 mu g/mL. Precision and accuracy values of the method were calculated as lower than 4.97% and +/- 5.68, respectively and the recovery of LP from rabbit plasma was higher than 91.1%. In addition, stability studies of LP in rabbit plasma were carried out and demonstrated its good stability at-20 degrees C and at room temperature. The developed and validated method was successfully applied for estimating the pharmacokinetic parameters of LP following oral administrations of a single 10mg LP/kg to rabbits and it could be concluded that the method can be applied to clinical trials. Copyright (c) 2014 John Wiley & Sons, Ltd.