Bioanalytical method development, validation and quantification of flupirtine maleate in rat plasma by liquid chromatography-tandem mass spectrometry.

A simple, highly sensitive, precise and accurate high-performance liquid chromatographic (LCMSMS) method with mass detection was developed and validated for the rapid quantification of flupirtine (CAS 75507-68-5) in rat plasma samples. The chromatographic separation was achieved with a reverse phase column (4.6 x 50 mm, 5 microm) and the mobile phase consisted of cyanomethane and 5 mM ammonium formate buffer pH 4.5 (70:30 v/v) as eluent, at a flow rate of 0.6 mL/min. Labetalol (CAS 36894-69-6) was used as an internal standard. The effluence was ionized by positive electrospray ionization and measured by mass spectrometry. The retention times of flupirtine and labetalol were found to be 2.16 and 1.66 min respectively. The calibration curve was linear (r2 > or = 0.99) ranging from 0.98 to 1000 ng/ml and the lower limit of quantification was 0.98 ng/ mL. Inter-day and Intra-day precision were lower than 5% (CV) and accuracy ranged from 90 to 110% in terms of percent accuracy. Mean extraction recovery was found to be above 86.5%. The method was successfully applied for evaluation of the pharmacokinetic profile of flupirtine in male Sprague-Dawley rats and validated for excellent selectivity, accuracy, precision, recovery and stability.