Today we’re going to have a chat about drugs, and how the medication you’re likely taking could lead to a false-positive on a urine drug screen (UDS). This isn’t a new topic, but it becomes more important the longer the common immunoassay drug tests are in use. A wide variety of “routinely prescribed medications” have appeared as false-positives in UDS tests over the past couple of decades.
I’m going to refer to a set of documents going back to the year 2010, here, with the latest popping up in August of 2018. In August of 2018 we’ve got a single confirmation that common UDS testing can give false-positives in the presence of mexiletine. That’s a drug given for the treatment of irregular heartbeat (arrhythmia).
This paper was called False-positive amphetamine results on several drug screening platforms due to mexiletine. It was published in the August 2018 issue of Clinical Biochemistry, with DOI:10.1016/j.clinbiochem.2018.05.013 by Christine L.H.Snozek et all.
Then we’ve got a paper published by Oxford University Press in the year 2014 called “False-positive interferences of common urine drug screen immunoassays: a review.” You’ll find that paper with DOI:10.1093/jat/bku075 in June of 2014.
That 2014 report shows 62 references to additional reports in which a number of drugs have been shown to appear as false-positives on UDS immunoassay tests. In 2014, researcher Alec Saitman refers to the following as a “generally accepted practice”. This report, said Saitman, supported “that immunoassay positive results are considered presumptive until confirmed by a second independent chemical technique.”
Perhaps the most comprehensive and detailed report that’s still used as a reference point here in 2019 is the report “Commonly prescribed medications and potential false-positive urine drug screens.” Nearly a decade after this research was released, immunoassay drug tests are still used around the world.
In the formulary and nonprescription list of reported false-positives, we’ve got the following. Brompheniramine, bupropion, chlorpromazine, clomipramine, dextromethorphan, diphenhydramine, doxylamine, ibuprofen, naproxen, promethazine, and quetiapine.
Prescription drugs like Bupropion, Clomipramine, Sertraline, Trazodone, and Venlafaxine appeared. Chlorpromazine appeared along with Promethazine, Quetiapine, and Thioridazine. The list included Dextromethorphan, Verapamil, and Ranitidine as well.
False-positive results pointed toward the presence of amphetamine and methamphetamines, as well as methadone, opioids, phencyclidine, barbiturates, cannabinoids, and benzodiazepines.
This research continues to expand – the list continues to grow. Now that we’re more attuned to the way our bodies and brains work, and (very necessary) medications continue to be prescribed, it’s more important than ever to find a new method for inexpensive yet accurate drug testing. Let us know if you’ve figured out how to make it happen!