Psychiatric and non-psychiatric drugs causing false-positive amphetamines urine test in psychiatric patients: a pharmacovigilance analysis using FAERS.

Immunoassay urine drug screen (UDS) is frequently used in clinical practice for initial screening process, being generally available, fast, and inexpensive. Exposure to widely prescribed drugs might determine false-positive UDS amphetamines, leading to diagnostic issues, wrong therapeutic choices, impairment of physician-patient relationship, and legal implications. To summarize and comment on a comprehensive list of compounds responsible for UDS false positives for amphetamines, we conducted a literature review on PubMed along with a comparison with Real-World Data from the Food and Drug Administration Adverse Event Reporting System (FAERS) database analysis between 2010 and 2022. Forty-four articles and 125 Individual Case Safety Reports (ICSR) involving false-positive amphetamine UDS in psychiatric patients were retrieved from FAERS. False-positive results were described in literature for antidepressants, atomoxetine, methylphenidate, and antipsychotics, but also for non-psychiatric drugs of common use, such as labetalol, fenofibrate, and metformin. Immunoassay method is usually responsible for false-positive results, and in most cases, mass spectrometry (MS) does not eventually confirm the UDS positivity. Physicians should be aware of immunoassays' limitations and when turning to a confirmatory test. Any new cross-reaction should be reported to pharmacovigilance activities.