Method Development and Validation for Simultaneous Determination of Ebastine and Its Active Metabolite Carebastine in Human Plasma by Liquid Chromatography-Tandem Mass Spectrometry and Its Application to a Clinical Pharmacokinetic Study in Healthy Chinese Volunteers.

A simple LC-tandem mass spectrometry (MS/MS) method to determine ebastine and carebastine (active metabolite) in human plasma was developed and validated. Analytes and internal standards were precipitated by protein precipitation and separated on Synergi Hydro-RP 80A column (4 mu m, 50 mm x 2.0 mm; Phenomenex) by gradient elution with mobile phase A comprising 0.1% formic acid in 5 mmammonium acetate (NH4Ac) and B comprising 100% methanol at a flow rate 0.4 mL/min. Ions were detected in positive multiple reaction monitoring mode, and they exhibited linearity over concentration range 0.01-8.0 and 1.00-300 ng/mL for ebastine and carebastine, respectively. A clinical pharmacokinetic study was conducted in healthy Chinese volunteers under fasting and fed conditions after a single oral administration of 10 mg ebastine. The maximum plasma concentration (C-max), time toC(max)(T-max) and elimination half-life for ebastine were 0.679 +/- 0.762 ng/mL, 1.67 +/- 1.43 h and 7.86 +/- 6.18 h, respectively, whereas these for carebastine were 143 +/- 68.4 ng/mL, 5.00 +/- 2.00 h and 17.4 +/- 4.97 h, respectively under fasting conditions; the corresponding values under fed conditions were 4.13 +/- 2.53 ng/mL, 3.18 +/- 1.09 h and 21.6 +/- 7.77 h for ebastine and 176 +/- 68.4 ng/mL, 6.14 +/- 2.0 h and 20.0 +/- 4.97 h for carebastine.