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