A simple bioanalytical assay for determination of montelukast in human plasma: application to a pharmacokinetic study.

An analytical method based on high-performance liquid chromatographic (HPLC) was developed for the determination of montelukast in human plasma using mefenamic acid as an internal standard. After precipitation of plasma proteins with acetonitrile, chromatographic separation was carried out using a Zorbax Eclipse XDB C8 (150 mm x 4.6 mm i.d., 5 microm) with mobile phase consisted of methanol-acetonitrile-0.04M disodium hydrogen orthophosphate (22:22:56, v/v, pH 4.9). The wavelengths of fluorescence detection were set at 350 nm for excitation and 450 nm for emission. The linearity was confirmed in the concentration range of 5-1000 ng/ml in human plasma. Intra- and inter-day accuracy determined from quality control samples were 101.50 and 107.24%, and 97.15 and 100.37%, respectively. Intra- and inter-day precision measured as coefficient of variation were < or =4.72 and < or =9.00%, respectively. Extraction recoveries of drug from plasma were >48.14%. The protocol herein described was employed in a pharmacokinetic study of tablet formulation of montelukast in healthy Thai male volunteers.