ASSAY-METHODS FOR SUFENTANIL IN PLASMA - RADIOIMMUNOASSAY VERSUS GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Background. The terminal pharmacokinetic parameters of sufentanil have , until now, been poorly characterized. This is probably because of th e poor sensitivity or unreliability of the assay methods used. Radioim munoassay (RIA) can be a very helpful assay method for sufentanil. How ever, before application to key pharmacokinetic studies, it requires a dequate validation, eg., by comparison with a method of proven sensiti vity and specificity, such as gas chromatography-mass spectrometry (GC -MS). Methods: Spiked control plasma samples and 135 plasma samples ob tained from five patients receiving intravenous doses of 500 or 750 mu g sufentanil, as a 10-20-min infusion, were analyzed by an improved, s ensitive RIA and capillary GC-MS. Results. Both techniques had compara ble limits of quantitation (0.02 ng/ml). Between-day coefficients of v ariation in the 0.05-10-ng/ml concentration range were 8.5-10.5% for t he RIA and less than 10% for the GC-MS method. The patient plasma conc entrations determined by RIA (y) and GC-MS (x) showed a good agreement (y = 1.016x + 0.002) and a correlation coefficient of 0.97. Conclusio ns. The results demonstrate the validity of the improved RtA method fo r the determination of sufentanil plasma concentrations.