AN ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR URINARY SCREENING OF FENTANYL CITRATE ABUSE

An enzyme-linked immunosorbent assay (ELISA) for quantitation of urina ry fentanyl was evaluated as a screening tool for detecting abuse of t his potent narcotic. The assay was found to have reproducible calibrat ion curves from 0.5 to 10 ng/mL and a limit of detection of 0.5 ng/mL. Interference by proteins, glucose, or pH was negligible. The assay wa s specific for fentanyl with little cross-reactivity against despropio nyl fentanyl and norfentanyl metabolites, other analgesics and common drugs of abuse. To evaluate its use in humans, urines were collected f rom 57 normal individuals, 48 patients seen in the Emergency Departmen t, and 18 surgical patients receiving either low (50 mu g) or moderate fentanyl dosage (200 and 250 mu g) for routine anesthesia. In patient s receiving 50 mu g (a dose consistent with early abuse), urinary fent anyl was detectable for 3 to 10 h post administration. In patients rec eiving 200 or 250 mu g (a dose more consistent with addiction), urinar y fentanyl was detectable for longer time periods (>24 h). These resul ts indicate that the ELISA is sensitive for the detection of recent fe ntanyl exposure under conditions likely to mimic those in abuse and ad diction. The assay is simple to perform, reliable, and can be used to screen urine specimens prior to gas chromatography/mass spectrometry ( CC/MS) confirmation.