From the Research
Promethazine and False Positive Results for Methamphetamine
- Promethazine, a phenothiazine derivative, can cause false-positive results for urine amphetamines using the EMIT II Plus Monoclonal Amphetamine/Methamphetamine Immunoassay 1
- Thirty-six percent of patients taking promethazine had false-positive test results for urine amphetamines, and 64% of patients showed cross-reactivity greater than 20% higher than the blank calibrator rate 1
- However, no promethazine-induced false-positive results were seen with the EMIT II Plus, Triage, and TesTcard 9 amphetamine assays, or the Triage methamphetamine assay 1
- The study suggests that promethazine metabolite(s), and not the parent compound, are the likely cause of these urine false-positive results obtained with EMIT II Plus Monoclonal Amphetamine/Methamphetamine Immunoassay 1
Other Substances Causing False Positive Results
- Ma-huang (Ephedra sinica), an herbal drug, can cause false-positive reactions for amphetamine/methamphetamine on the Triage panel 2
- Phenylephrine, an α(1)-adrenergic agonist, can cross-react with methamphetamine in urine drug screening (UDS) performed by immunoassay, resulting in false-positive results 3
- Metoprolol, a beta-blocker, can cause false positive results in amphetamines and MDMA immunoassays 4
Promethazine Abuse and Misuse
- Promethazine has a misuse potential, especially in adolescents, and its abuse has been reported to the European Monitoring Agency Adverse Drug Reactions database 5
- The analysis of promethazine data showed increasing levels of misuse/abuse/dependence issues over time, with a high number of fatalities described 5