Analysis of desmethylmethsuximide using high-performance liquid chromatography.

Analysis of desmethylmethsuximide by high-performance liquid chromatography (HPLC) is described. After adding an internal standard (IS), 200 microliters of plasma was buffered to pH 4.5 and extracted with dichloroethane. The organic solvent was then evaporated to dryness and the residue reconstituted in 100 microliters of mobile phase prior to injecting a 20 microliters aliquot onto a Hypersil 5 MOS column, which was eluted with acetonitrile/acetate buffer (pH 5.5) 36:64 vol/vol. Constituents were separated in approximately 8 min. Using this method, down to 1.0 mg/L of desmethylmethsuximide in plasma can be accurately determined. The method is suitable for therapeutic monitoring of desmethylmethsuximide in patient samples.