Vortioxetine use may cause false positive immunoassay results for urine methadone

Background: Urine immunoassays are frequently employed for methadone screening because they are relatively inexpensive and widely available. However, immunoassays are notoriously prone to false positives. We report that the use of vortioxetine (Trintellix (R) in the USA and Canada, Brintellix (R) worldwide) could cause false positives in the Roche KIMS Methadone II Urine immunoassay (MDN2). Methods: We performed a spiking study using a parent drug vortioxetine concentration of 7500 ng/ml. Results: Urine specimens from seven patients on typical vortioxetine doses tested positive for methadone in the Roche assay but negative for methadone in a confirmatory (GC/MS) assay and two other immunoassay platforms. Because of the pharmacokinetics of vortioxetine and the high cross-reactivity of a metabolite in the MDN2 assay, routine use of the drug could cause false positives even without detectible parent drug in the urine. Conclusions: Vortioxetine is commonly prescribed for mood disorders, which have high prevalence in patients treated for opioid addiction. For that reason, it is important that clinicians are aware of this interference.