What drugs and food can interact with urine testing?

Health workers, law enforcement agents, coaches, employers, and parents are increasingly turning to drug tests to detect the use of illicit drugs. While this testing creates a sense of accountability in workers, citizens, and teenagers, the initial tests are only screening tests and can cross react with other medications and even some foods. A viewer wrote in and said that he had eaten two poppy seed bagels and is scheduled to have a drug test over the next three days, what is the risk it will come back positive?


Click to enlarge chart.

The short answer is yes and no, the initial urine screening test may come back positive over the next day or so but the confirmation test is very unlikely to be positive. The screening tests have high sensitivity which means that they will detect most people who have taken illicit drugs within the past several days but has lower specificity. This means that there are people who did not take the illicit drugs that get a positive test and those need to be confirmed with a higher quality and more expensive test like gas chromatography or mass spectrometry. So while you will not ultimately be denied a job, you may have to do the first test and then come back for a more specific test that same day. This can be nerve racking for the viewer while the results are beig processed. So the best thing that the viewer can do is alert the tester that they had poppy seeds and to test on the third day rather than days 1 or 2 where the chance of detection will be much less.

I have put together a comprehensive chart of the drugs and food that can interact with different illicit substance drug tests but I will just highlight a few of them here. Ranitidine (Zantac), an over the counter heartburn drug, and two different over the counter decongestants (phenylpropanolamine and Vicks Vapor Inhaler) can show up as methamphetamine. Phenylpropanolamine is now available behind the counter because this decongestant can be chemically altered to create methamphetamine so that make sense. In another example, two over the counter antihistmaines called doxylamine and diphenhydramine and an over the counter cough suppressant called dextromethorphan can cross react with methadone. So try to avoid these over the counter drugs if you think you will be taking a drug test in the next 3 to 5 days. In many of the other cases, the drugs are chronic therapies for Parkinson’s disease, depression, psychosis and infections and you should not stop the drugs because you have a drug test coming up. You just need to alert the testers that you are taking a drug that might interact and know that the more sophisticated confirmatory tests will be able to tease this out.

The kits can be helpful in some circumstances by identifying not only that an illicit drug was taken but what the illicit drug was. Parents need to be aware that some false positives can turn up and that using the tests when you have a high suspicion of impairment due to recent drug use is best. Concentrations of the illicit drugs in the blood or urine can start to go down within 12-24 hours up to 3-5 days and may or may not be detectable if you wait too long. The tests do not tell you how much of the illicit drug your child has ingested and cannot tell you if your child meant to take the drug or if they were drugged by another person at a party. So parents just need to be sure that they know what the tests can and cannot provide them.

By Michael White; Dept. Of Pharmacy Practice, UConn School Of Pharmacy

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