Commonly prescribed medications and potential false-positive urine drug screens

American Journal of Health-System Pharmacy, Vol. 67, Issue 16, 1344-1350
Copyright © 2010 by American Society of Health-System Pharmacists
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Articles by Palmer, T. A.

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Clinical Consultation
Commonly prescribed medications and potential false-positive urine drug screens
Nancy C. Brahm, Lynn L. Yeager, Mark D. Fox, Kevin C. Farmer and Tony A. Palmer
NANCY C. BRAHM, PHARM.D., M.S., is Clinical Associate Professor, Department of Pharmacy Practice: Clinical and Administrative Sciences, College of Pharmacy; LYNN L. YEAGER, M.L.I.S., is Assistant Professor, College of Medicine; MARK D. FOX, M.D., PH.D., M.P.H., is Associate Dean for Community Health and Research Development, School of Community Medicine, College of Medicine; KEVIN C. FARMER, PH.D., is Associate Professor, Department of Pharmacy Practice: Clinical and Administrative Sciences, College of Pharmacy; and TONY A. PALMER, B.S.PHARM., M.B.A., is Clinical Associate Professor, Department of Pharmacy Practice: Clinical and Administrative Sciences, College of Pharmacy, University of Oklahoma, Tulsa

Address correspondence to Dr. Brahm at the Department of Pharmacy Practice: Clinical and Administrative Sciences, College of Pharmacy, University of Oklahoma, 4502 East 41st Street, 2H17, Tulsa, OK 74135-2512 (nancy-brahm@ouhsc.edu).


Purpose. The implications of potential false-positive urine drug screen (UDS) results for patients receiving commonly prescribed medications were evaluated.
Summary. A comprehensive literature review was conducted to identify false-positive UDSs associated with all clinic formulary medications, as well as common nonprescription medications. The references of each report describing a medication whose use was associated with false-positive UDS results were also reviewed. If a class effect was suspected, additional agents in the category were searched. A total of 25 reports of false-positive UDS results were identified. Categories of medications included antihistamines, antidepressants, antibiotics, analgesics, antipsychotics, and nonprescription agents. Reports of false-positive results were found for the following formulary and nonprescription medications: brompheniramine, bupropion, chlorpromazine, clomipramine, dextromethorphan, diphenhydramine, doxylamine, ibuprofen, naproxen, promethazine, quetiapine, quinolones (ofloxacin and gatifloxacin), ranitidine, sertraline, thioridazine, trazodone, venlafaxine, verapamil, and a nonprescription nasal inhaler. False-positive results for amphetamine and methamphetamine were the most commonly reported. False-positive results for methadone, opioids, phencyclidine, barbiturates, cannabinoids, and benzodiazepines were also reported in patients taking commonly used medications. The most commonly used tests to screen urine for drugs of abuse are immunoassays, even though false-positive results for drugs of abuse have been reported with a number of these rapid-screening products. Results from such tests should be confirmed using additional analytical methods, including gas chromatography–mass spectrometry.

Conclusion. A number of routinely prescribed medications have been associated with triggering false-positive UDS results. Verification of the test results with a different screening test or additional analytical tests should be performed to avoid adverse consequences for the patients.

http://www.ajhp.org/cgi/content/abstract/67/16/1344