Determination of carisoprodol and meprobamate in oral fluid

The determination of carisoprodol and its metabolite meprobamate in oral fluid using solid-phase extraction and liquid chromatography with tandem mass spectral detection (LC-MS-MS) and its application to authentic specimens is described. The method employs collection of oral fluid with the Quantisal device, extraction using cation exchange/hydrophobic solid-phase columns, and LC-MS-MS in positive ion electrospray mode. The method was fully validated using various parameters, including selectivity, linearity, accuracy, intra-day and inter-day imprecision, drug recovery from the collection pad, limit of quantitation and matrix effects. The method was applied to both routine research specimens and an authentic specimen taken from an individual prescribed a daily dose of 350 mg carisoprodol following surgery.