Drug testing is the practice of screening urine or blood samples for the presence of illegal drugs. These screening tests are routinely performed by schools, parents and companies for the purpose of determining if those tested are abusing substances such as opiates, phencyclidine (PCP), cocaine, marijuana or amphetamines. Drug tests are very unlikely to miss the presence of a substance; however, a false positive, a positive result even when no illegal substance is present, does occur in approximately 1 to 2.5 percent of tests, according to NetWellness.org.
Over-The-Counter Medications
A number of over-the-counter medications can cause a false positive result on a drug test. Common cough, cold and allergy medications may contain forms of codeine, similar to the more powerful morphine. These substances can result in a false positive for opiates or amphetamines.
Over-the-counter products containing ibuprofen, a common pain reliever and anti-inflammatory, have been known to cause a positive result for marijuana. Some over-the-counter cough medicines that contain dextromethorphan, a common cough suppressant, can trigger a positive result for opiates.
Over-the-counter diet pills used as appetite suppressants may also affect a drug test. Diet pills often contain substances that are similar to opiates or amphetamines and can therefore result in a positive drug screen.
Prescription Medications
Some prescription medications can also cause a false positive drug test. Some medications prescribed to treat depression, such as sertraline, may cause a positive result. Amitriptyline, another antidepressant medication, has been known to test positive for opiates. Imipramine, a medication classified as a tricyclic antidepressant, may also test positive for opiates. Diazepam, an anti-anxiety prescription medication, has been reported to cause erroneous results on PCP drug screens.
Food and Supplements
There are even some food products, natural herbal supplements and nutritional supplements that can cause a false positive result on a drug screen. Poppy seeds, tiny blue-gray seeds, are harvested from the opium plant and used in cooking and baking. Poppy seeds add a nutty flavor to cakes and breads, but because they come from the opium plant, they can trigger a positive drug test.
Hemp-seed oil is available as a nutritional supplement and may be used to make cakes, cookies, cheese and bread. Eating these foods, however, can result in a drug test positive for marijuana.
Ephedra is an herbal supplement that is extracted from the Ephedra sinica plant. Used along with caffeine as a dietary supplement to elicit weight loss, ephedra was found in many commercially available products. Ephedra, similar in chemical structure to ephedrine, stimulates the central nervous system and causes the airways to dilate and the heart to beat faster. Due to a number of reported serious side effects, the United States Food and Drug Administration banned the use of ephedra in 2004. Using products containing ephedra will cause a false positive result for an amphetamine drug test.
