An Enzyme-Linked Immunosorbent Assay for Urinary Screening of Fentanyl Citrate Abuse*

An enzym e-linked im m unosorbent assay (ELISA) for quantitation of uri­ nary fentanyl was evaluated as a screening tool for detecting abuse of this po ten t narcotic. T he assay was found to have reproducible calibration curves from 0.5 to 10 ng/mL and a lim it of detection of 0.5 ng/mL. In te r­ ference by proteins, glucose, or pH was negligible. T he assay was specific for fentanyl w ith little cross-reactivity against despropionyl fentanyl and norfentanyl m etabolites, other analgesics and common drugs of abuse. To evaluate its use in hum ans, urines w ere collected from 57 norm al individu­ als, 48 patien ts seen in the E m ergency D epartm ent, and 18 surgical patients receiving either low (50 (xg) or m oderate fentanyl dosage (200 and 250 jxg) for routine anesthesia. In patients receiving 50 |xg (a dose consis­ ten t w ith early abuse), urinary fentanyl was detectable for 3 to 10 h post adm inistration. In patients receiving 200 or 250 (Jtg (a dose m ore consistent w ith addiction), urinary fentanyl was detectable for longer tim e periods (>24 h). T hese results indicate that the ELISA is sensitive for the detection of recent fentanyl exposure under conditions likely to mimic those in abuse and addiction. T he assay is sim ple to perform, reliable, and can be used to screen urine specim ens prior to gas chrom atography/m ass spectrom etry (GC/MS) confirmation.