Some people whose urine tests positive for tetrohydrocannabinol--THC--are shocked to be told they failed the drug test for marijuana, which they've never used. According to pharmacologist Karen E. Moeller and colleagues in their 2008 article for "Mayo Clinic Proceedings," individuals who have taken nonsteroidal anti-inflammatory drugs, or NSAIDs, as well as those who have taken some proton pump inhibitors, may test positive for THC. In a 2010 article in "Pain Physician," Laxmaiah Manchikanti, M.D. and colleagues note those taking dronabinol, sold under the brand name Marinol, will get a false positive for THC on a urine drug screen, even if they are not abusing marijuana.
NSAIDs
Common NSAIDs such as ibuprofen or naproxen may lead to a false positive in a urine drug screen, says Dr. E. Chris Vincent, in his 2006 article for the "Journal of Family Practice." The reasons for these results are unknown.
According to Dr. Moeller, the prescription drug tolmetin, which has the brand name Tolectin or Tolectin DS, is an NSAID which can also give a false positive for THC on a urine drug screen. This drug is sometimes used for arthritis pain.
Pantoprozole
According to Dr. Manchikanti, the prescription drug pantoprazole, also known as Protonix, may give a false positive in a drug screen, although the reason for such a result is unknown. Pantoprazole is a proton pump inhibitor, a drug taken by individuals with chronic heartburn or ulcer disease. Individuals taking pantoprazole concerned about obtaining a false positive should inform the test taker of their proton pump inhibitor use and bring the prescription bottle with them to the test site to show the tester.
Dronabinol
Dronabinol, or Marinol, is a drug given for severe nausea and vomiting, such as is experienced by cancer patients receiving chemotherapy, but this synthetic marijuana-like legal drug also gives a false positive for THC, says pathology and laboratory medicine professor Amitava Dasgupta of the University of Texas in Houston. Dronabinol converts into a metabolite of marijuana in the body and thus yields a positive test for marijuana in urine drug screening.
Efavirenz
In a 2007 article by Gary M. Reisfield, M.D., of the University of Florida Health Science Center in Jacksonville, Florida, published in "Annals of Clinical & Laboratory Science," notes that efavirenz, sold under the brand name Sustiva, a drug used to treat patients with AIDS, may give a false positive for THC. They say a confirmatory test will usually rule out marijuana abuse.
References
- "Medical Laboratory Observer"; False-Positive DOA Testing Results Due to Prescription Medications; Amitava Dasgupta, Ph.D.; October 2009
- "Pain Physician"; Protocol for Accuracy of Point of Care (POC) or In-Office Urine Drug Testing (Immunoassay) in Chronic Pain Patients; Laxmaiah Manchikanti, M.D., et al.; 2010
- "Journal of Family Practice"; What Common Substances Can Cause False Positives on Urine Screens for Drugs of Abuse?; E. Chris Vincent, M.D., Arthur Zebelman, Ph.D.;, and Cheryl Goodwin, MLS; October 2006
- "Annals of Clinical & Laboratory Science"; Rational Use and Interpretation of Urine Drug Testing in Chronic Opioid Therapy; Gary M. Reisfield, Elaine Salazar and Roger L. Bertholf; 2007
- "Mayo Clinic Proceedings"; Urine Drug Screening; Karen E. Moeller, PharmD; et al.; January 2008
