Is Dextromethorphan a Concern for Causing a False Positive During Urine Drug Screening?

Abstract

The initial screening for drugs of abuse invariably poses the risk for false positives due to cross-reactivity. The over-the-counter antitussive medication dextromethorphan (DXM) can cause false-positive results for phencyclidine (PCP) upon urine drug screening (UDS). It is believed that DXM can also cause a false positive for opiates, presumably due to structural similarities. This could have serious implications, as DXM abuse is reported to be increasing. However, many of these claims are anecdotal, as no fully comprehensive studies exist. Furthermore, what studies have been completed reveal that DXM does not cause a false positive for opiates, despite their similarity in structure. Laboratories have established cut-off limits for opiates for the initial screen, and like all presumptive positives, confirmation with more sensitive methods are strongly recommended to rule out false positives. * DXM : dextromethorphan PCP : phencyclidine UDS : urine drug screening DXO : dextrorphan CNS : central nervous system NMDA : N-methyl-D-aspartate DAU : drugs of abuse-urine EMIT : enzyme multiplied immunoassay technique FPIA : fluorescence polarization immunoassay RIA : radioimmunoassay KIMS : kinetic interaction of microparticles in solution CEDIA : cloned enzyme donor immunoassay SAMHSA : Substance Abuse and Mental Health Services Administration GC-MS : gas chromatography-mass spectrometry LC-MS : liquid chromatography-mass spectrometry HPLC : high-performance liquid chromatography