Analysis of zolpidem in human plasma by high-performance liquid chromatography with fluorescence detection: Application to single-dose pharmacokinetic studies

Zolpidem, an imidazopyradine hypnotic agent, can be quantitated by high- performance liquid chromatography (HPLC) with fluorescence detection. After the addition of a structurally related internal standard (propyl-zolpidem), plasma samples were double-extracted at neutral pH with toluene-isoamyl alcohol or benzene-isoamyl alcohol. The organic extracts were evaporated to dryness, reconstituted with mobile phase, and analyzed by HPLC using a C-18 reversed-phase column, a mobile phase of acetonitrile-50mM potassium dihydrogen phosphate (50:50), and fluorescence detection with excitation and emission wavelengths of 254 and 390 nm, respectively. The lower limit of reliable quantitation was in the range of 1-2.5 ng/mL. The method is applicable to single-dose pharmacokinetic studies of zolpidem in humans.