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 and methylphenidate, antipsychotics, but also for non-psychiatric drugs of common use, like labetalol, fenofibrate and metformin. Immunoassays method is usually responsible for false positive results and in most cases mass spectrometry (MS) do 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.