Microdetermination of emtricitabine in human plasma by liquid chromatography/tandem mass spectrometry

A simple, precise, and rapid LC/MS/MS method was developed and validated for the quantification of emtricitabine in human plasma using lamivudine as the internal standard (IS). The method involves liquid-liquid extraction of emtricitabine and the IS in diethyl ether-ethyl acetate (50 + 50, v/v) from 0.1 mL human plasma. A Kromasil C18 (150 x 4.6 mm, 5 microm particle size) analytical column was used for the chromatographic separation under isocratic conditions. The parent --> product ion transitions for emtricitabine (m/z 248.0 --> 130.0) and the IS (m/z 230.1 --> 112.0) were monitored on a triple-quadrupole mass spectrometer, operated in the multiple reaction monitoring positive ion mode. The method was validated over the concentration range of 29.2-3110 ng/mL for emtricitabine, with a total chromatographic run time of 1.5 min. Acceptable precision and accuracy were obtained for the concentrations used to prepare the standard curves. The applicability of the method was demonstrated by a pharmacokinetic study conducted with 43 healthy volunteers who were administered a capsule formulation containing 200 mg emtricitabine.