Drug Test Interaction With Medicines And Foods Be aware that certain foods and over-the-counter medications can cause you to test "positive" for various kinds of drugs. Poppy seeds, for example, can show up on a drug test as morphine. Cold remedies that contain codeine can also cause a positive result for morphine. Valium reportedly can produce erroneous indications of PCP (Phencyclidine), and other cold remedies can apparently produce false reports of methamphetamine usage. Dextromethorphan can produce a falsely positive qualitative urine opiate screening. The widespread availability of hemp-containing products, including everything from hemp-seed oil nutritional supplements to hemp-seed candy, cookies, cheese, bread, cooking oil, and general seasoning, means that ingesting ANY of these products could potentially cause a false positive result on a test for marijuana. Ibuprofen, contained in Advil, Nuprin, and Mortin, can make a positive result for marijauna. The EMIT test (an immunoassay test) has therefore been changed to use a different enzyme to eliminate false positives due to Ibuprofen. Ibuprofen in very high doses will still interfere with both the EMIT and the GC/MS (Gas Chromatograph/Mass Spectrometer) test. Ibuprofen: Ibuprofen is a common pain reliever that (even in low dosages) used to cause a false THC positive on the EMIT test. The EMIT has been changed to use a different enzyme to eliminate false positives due to Ibuprofen. Ibuprofen in very high doses will still interfere with both the EMIT and the GC/MS. There is some conflicting data here because some sources say that the GC/MS tests can distinguish between Ibuprofen and THC (as well as other over-the-counter drugs). Common over the counter cold, asthma, and allergy remedies and diet pills such as Diatec, Dexatrim, Cotylenol, Triaminic, Primatene, Bronkotabs, and Nyquil can show up as positive for amphetamines. Vicks Formula-44, Demerol, Mydol, Primatene-M and common prescription antidepressants such as Elavil and Tofanil can show up as positive for opiates such as opium and heroin. Ephedra, also known as Ephedra Alkaloids or 'MaHuang Extract' has a chemical structure which is closely related to amphetamine, and can reportedly give a false positive for amphetamines. Often sold as an 'energy pill' it is an effective decongestant in low doses. Valerian root is reported to cause false positives for benzodiazepines. Other herbal supplements such as Kava Kava and St Johns Wort may also affect body chemistry such that false positives are produced. Zoloft (WellbutrinÂ®) is reported to cause false positives in urine screens, although for what specific substance isn't clear. Primatene can also show up as positive for barbiturates, and Benadryl can show up positive for Methadone. Some additional over the counter medicines that may cause various kinds of drug test interactions include Alka-Seltzer plus, Allerest, Bronkaid, Contac, Donnagel, Sinuntab, and Sudafed.