LC-MS-MS Quantitative Determination of Brivudine in Human Plasma and Its Application to Pharmacokinetic Studies

A sensitive and specific liquid chromatography-electrospray ionization-tandem mass spectrometry method has been developed and validated for the identification and quantification of brivudine in human plasma using diclofenac as an internal standard. The method involves extraction with ethyl acetate. The analyte was separated on a C(18) column and analyzed in multiple reaction monitoring mode with a negative electrospray ionization interface using the [M-H](-) ions, m/z 332.8 -> m/z 80.9 for brivudine, m/z 293.6 -> m/z 249.5 for diclofenac. The method was validated over the concentration range of 5.54-2,836 mu g L(-1) for brivudine. The intra-and inter-day precisions were less than 8.91% in terms of relative standard deviation (RSD), and the accuracy was within -4.22% in terms of relative error (RE). The lower limit of quantification (LLOQ) was 5.54 mu g L(-1) with acceptable precision and accuracy. There were almost no matrix effects. Recovery of brivudine spiked in drug-free plasma was higher than 77.17%. The method was used to study the pharmacokinetic profile of brivudine in human plasma after oral administration of brivudine tablets.