We have heard speculation that DXM may cause false positives for both PCP and Opiates in standard urine tests. After doing a bit of research on the web we found a small handful of references on the topic. Most of these support the possibility that DXM may cause false positives, but the only peer reviewed journal article refutes that normal doses of DXM cause false positives for Opiates.

Erowid has received one report of an individual who tested positive for PCP a few hours after ingesting DXM.(1) Another report was posted to usenet where an individual purchased and ingested a medium-high dose DXM powder. He ended up in the emergency room where he tested positive for both PCP and Opiates. His conclusion was that the DXM powder he had purchased was not pure, but there is every reason to believe that it may have been pure DXM which caused both of these false positives.(2)

The one peer reviewed study which we found tested normal label recommended cough suppressant doses of DXM. They tested twenty individuals after either 20 or 40 mg doses of DXM and found that none tested positive for Opiates 72 hours later (using EMIT).(3) Obviously this is a significantly lower dose than most recreational users choose. The primary thing this tells us is that it might be difficult to use medicinal DXM use as an excuse for testing positive for Opiates.

And just to confuse the issue, we have heard from over twenty individuals who say that they have undergone urine tests while on DXM and that they passed the tests with no problems.

Even though DXM is legal, it can be very difficult (if not impossible) to explain to an employer or parole officer that you haven't, in fact, ingested PCP, but were instead using DXM recreationally at high doses. Follow-up tests can (and should) be performed which would be able to differentiate between DXM and PCP, but in the case of pre-employment tests for instance, they may not bother with the follow-up.

The fact that there is so little available data means that this question is still very much up in the air. If anyone has had an experience with using DXM before a drug test, whether it caused a false positive or not, please consider filling out an experience report letting us know how much DXM was taken, how long before the drug test, any information known about what type of drug test was used, and the results of the test (with as many details as possible).