Simultaneous determination of ebastine and its active metabolite (carebastine) in human plasma using LC-MS-MS

A sensitive and rapid LC-MS-MS method was developed for the simultaneous determination of ebastine and carebastine in human plasma. Solid-phase extraction was used to isolate the compounds from the biological matrix followed by separation on a Symmetry C18 column under isocratic conditions. The mobile phase was 10 mM ammonium formate in water/acetonitrile (40:60, v/v). Detection was carried out using a triple-quadrupole mass spectrometer in positive electrospray ionization and multiple reaction monitoring mode. The method was fully validated over the concentration range of 0.1-10 ng mL^-1 for ebastine and 0.2-200 ng mL^-1 for carebastine in human plasma, respectively. The lower limit of quantification (LLOQ) was 0.1 ng mL ^-1 for ebastine and 0.2 ng mL^-1 for carebastine. For ebastine and carebastine inter- and intra-day precision (CV%) and accuracy values were all within ±15% and 85-115%, respectively. The extraction recovery was on average 60.0% for ebastine and 60.3% for carebastine.