Analysis of doxylamine in plasma by high-performance liquid chromatography

A rapid and sensitive high-performance liquid chromatographic (HPLC) assay for the quantitative determination of doxylamine in plasma is described. The drug levels of doxylamine in plasma were monitored after the oral administration of a single 25-mg tablet of doxylamine succinate to each of 20 male volunteers. The compound was extracted from the plasma samples, concentrated under a nitrogen stream, and analyzed by HPLC using normal-phase chromatography with detection at 254 nm. The detection limit is approximately 5 ng/ml.