Drug Monitoring, Fentanyl, Screen, Urine - Fentanyl is an opioid analgesic with a potency approximately 80 times that of morphine. The test is a screening assay using a homogeneous enzyme immunoassay method of analysis. Therapeutic urine drug monitoring of fentanyl is important for ensuring compliance to treatment strategies, as well as ensuring non-diversion for illicit purposes. Urine or oral fluid are the specimens of choice for routine monitoring of patients taking prescription drugs.