Quantitative determination of cabergoline in human plasma using liquid chromatography combined with tandem mass...

A liquid chromatography/mass spectrometry (LC/MS) method using electrospray ionization (ESI) is described for the quantitative determination of cabergoline (N-[3-(dimethylamino)propyl]-N-(ethylamino)-carbonyl-6-(2-propenyl)- ergoline-8 beta-carboxamide) in human plasma. The method consists of liquid-liquid extraction after addition of deuterated internal standard, and reverse-phase liquid chromatography with electrospray ionization combined with tandem mass spectrometry (MS/MS). Using selected reaction monitoring, the method provides a quantitation limit of 1.86 pg/mL. Calibration curves acquired on five different days showed good linearity (r > 0.99) in the range 1.86-124 pg/mL and reproducibility of the slope (% relative standard deviation, RSD = 10.0). The intra-day precision, determined by assaying plasma containing four different concentrations of cabergoline processed in replicate, was found to range from 2.4 to 17.0% (RSD). The inter-day precision, evaluated for the same concentrations, ranged from 7.9 to 10.7% (RSD). The accuracy of the method, expressed as the percent ratio between found to added amount, was 99.1 +/- 10.2% (RSD = 10.3%, n = 78).