Bioanalytical Method Development, Validation and Quantification of Metaxalone 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 metaxalone (CAS Registry No, 1665-48-1) in rat plasma samples. The chromatographic separation was achieved with a reverse phase column Agilent XDB C18 (4.6×100 mm, 5μ) and the mobile phase consisted of methanol and 5 mm ammonium acetate buffer (80:20 v/v) as eluent, at a flow rate of 0.6 mL/min. Phenytoin (CAS Registry no, 57-41-0) was used as an internal standard. The effluence was ionized by positive electrospray ionization and measured by mass spectrometry. The retention time of metaxalone and phenytoin were found to be 1.60 and 1.83 min respectively. The calibration curve was linear (r2 > or = 0.99) ranging from 0.98 to 998 ng/ml and the lower limit of quantification was 0.98 ng/mL. Interday and Intraday 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 82%. The method was successfully demonstrated for evaluation of pharmacokinetic profile of metaxalone in male Sprague dawley rats and validated for excellent selectivity, accuracy, precision, recovery and stability.