Naltrexone is a medication primarily used to support individuals in their recovery from opioid and alcohol dependence. It functions by blocking the effects of opioids and reducing alcohol cravings. This article clarifies whether naltrexone typically causes false positives on drug tests, explains how drug tests work, outlines other common causes of false positives, and details steps to take if you receive an unexpected result.
Naltrexone and Drug Tests
Naltrexone generally does not cause a false positive result for commonly screened illicit drugs, such as opioids, amphetamines, or cannabis, on standard immunoassay drug tests. Naltrexone is an opioid antagonist, meaning it blocks opioid receptors rather than activating them. Its chemical structure is distinct enough from typical illicit substances to prevent cross-reactivity with the antibodies used in initial drug screenings. The primary metabolite of naltrexone, 6-beta-naltrexol, also typically does not interfere with these tests. While rare case studies suggest naltrexone or its minor metabolite, noroxymorphone, might sometimes cause a false positive for oxycodone on initial screens, this is not a common occurrence. Standard drug tests are not designed to detect naltrexone itself unless specifically included in a specialized testing panel.
How Drug Tests Work and Why False Positives Occur
Drug tests often involve a two-step process: an initial screening followed by a confirmatory test if the screen is positive. Initial screenings, commonly immunoassays, are designed for rapid and cost-effective detection of drug classes. These tests use antibodies that bind to specific drugs or their metabolites. If a substance in the sample binds to these antibodies above a certain cutoff level, the test registers a presumptive positive result. False positives can occur during this initial immunoassay screening when a substance with a similar chemical structure to a target drug causes the antibodies to react, even if the actual drug is not present. This cross-reactivity is a known limitation of immunoassay tests, which are highly sensitive but less specific. If an initial screen yields a positive result, a more accurate confirmatory test, such as Gas Chromatography-Mass Spectrometry (GC-MS) or Liquid Chromatography-Mass Spectrometry (LC-MS), is typically performed. These confirmatory tests precisely identify and quantify specific substances by their unique molecular fingerprints, virtually eliminating false positives.
Other Common Causes of False Positive Drug Tests
Since naltrexone does not commonly cause false positives, it is helpful to understand other substances that frequently do. Various over-the-counter and prescription medications can lead to false positives on initial drug screens due to structural similarities. For instance, common pain relievers like ibuprofen or naproxen can sometimes trigger false positives for THC or barbiturates. Decongestants containing pseudoephedrine or ephedrine may cause false positives for amphetamines.
Certain antidepressants, such as sertraline or bupropion, have also been reported to cause false positives for substances like benzodiazepines, LSD, or amphetamines. Even some foods, like poppy seeds, can lead to a false positive for opiates due to their natural morphine and codeine content. These examples highlight the importance of understanding potential cross-reactivity with common medications and dietary items.
Steps to Take After a False Positive
Receiving a false positive drug test result can be concerning, but there are clear steps to address the situation. Immediately inform the testing facility, employer, or relevant authority about all medications you are currently taking. This includes prescription drugs like naltrexone, over-the-counter medications, and any supplements. Providing documentation, such as a doctor’s note or prescription, can be helpful. The most important step is to request a confirmatory test. Confirmatory tests, such as GC-MS or LC-MS, are highly accurate and can differentiate between substances, thereby ruling out a false positive. Most employers and testing agencies are aware that initial screens can produce false positives and will accommodate a request for a confirmatory test. This will provide a definitive and accurate result regarding the presence of any substances.