Rapid and Sensitive LC-MS/MS Method for Quantification of Fexofenadine in Human Plasma -- Application to a Bioequivalence Study in Chinese Volunteers

A rapid and sensitive liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for the quantification of fexofenadine in human plasma, to conduct comparative bioavailability studies. Human plasma was extracted with a mixture of dichloromethane-diethyl ether (volume ratio 2:3) in a basic environment and the extract was separated on a C18 column with a mobile phase consisting of acetonitrile-methanol-10 mmol/L ammonium acetate (volume ratio 45:45:10). The analytes were detected via electrospray ionization (ESI) tandem mass spectrometry in the multiple-reaction-monitoring (MRM) mode. The linearity was within a range of 1-1000 ng/mL. The intra- and inter-day precision were <4.1% and <4.8%, respectively, and the accuracy was in the range of 95.0%-105%. The method was applied to the quantification of fexofenadine human plasma from 20 healthy male Chinese volunteers, according to a single dose, randomized, two-way crossover design with a two-week washout period. The mean values of major pharmacokinetic parameters of ρmax, AUC0-48, AUC0-ρ, Tmax, and t1/2 were determined from the plasma concentration. The analysis of variance (ANOVA) did not show any significant difference between the two products of fexofenadine and 90% confidence intervals fell within the acceptable range for bioequivalence.