Determination of alfentanil in serum by radioimmunoassay or capillary column gas-liquid chromatography. A comparison of the assays.

In view of recent controversies about the specificity and accuracy of radioimmunoassays (RIA) for morphine and alfentanil, we assessed the validity of an RIA for alfentanil by comparing it with a novel capillary column gas-liquid chromatographic (GLC) assay. The coefficients of variation for eight determinations of alfentanil in plasma or serum were approximately 2% at 2, 20, and 400 ng/ml with both assays. The assay comparison was done using 85 serum samples from patients given intravenous alfentanil. There was an excellent correlation between the assay results obtained by RIA and by GLC in the range of 10-1 825 ng/ml. The two assays can therefore be used interchangeably in pharmacokinetic studies.