Abstract

A simple, fast and accurate liquid chromatography–electrospray ionization-tandem mass spectrometry method was developed and validated for the quantification of cyclobenzaprine in human plasma. After a simple single-step liquid–liquid extraction with ethyl acetate, the analyte was separated in an Intersil ODS-3 column through isocratic elution with methanol–water containing 0.1% formic acid (80:20, v/v) at a flow rate of 0.2 ml/min and analyzed by mass spectrometry in the positive ion MRM mode. Good linearity was achieved from 0.04 to 50 ng/ml. The intra- and interday precisions were less than 12.1%, and accuracy ranged from 99.6 to 106.2%. The elimination half-lives (t_1/2 Z) after a single oral administration of 5, 10, and 15 mg cyclobenzaprine tablets were 25.5, 26.2, and 26.4 h, respectively. The means ofC_max and AUC increased proportionally to the cyclobenzaprine doses. The pharmacokinetics of cyclobenzaprine fit the linear dynamics of the cyclobenzaprine dose range in healthy Chinese volunteers.

Key words: Cyclobenzaprine, liquid chromatography, electrospray ionization, tandem mass spectrometry.