Determination of flunarizine in rat brain by liquid chromatography-electrospray mass spectrometry.

A rapid liquid chromatography-electrospray mass spectrometry (LC-ES-MS) assay for the determination of flunarizine (FZ) in rat brain has been developed. A C18 column and an isocratic elution were employed for the separation. Using post-column split, 64% of the eluent was introduced into the ES-MS system for detection. The [M+H]+ (m/z 406) and a fragmented ion (m/z 203) were detected using selected ion monitoring. The linear range of this assay was good, ranging from 0.05 to 5 microM (r2=0.99). The intra- and inter-day precisions showed relative standard deviations ranging from 1.4% to 2.0% and 1.3% to 2.9%, respectively. The application of this newly developed method was demonstrated by examining the pharmacokinetics of FZ in rat brain.