Naltrexone is prescribed for alcohol use disorder and opioid use disorder, either as a daily oral tablet or as a once monthly extended release injection sold under the brand name Vivitrol. A standard opiate immunoassay strip, the kind used in most pre employment and workplace drug test cups, is built to detect morphine and codeine. Naltrexone is an opioid antagonist, not an opioid, and it is not a federally controlled substance, so it does not cause a positive result on that strip. People who take it, or who manage employees and clients who take it, often still want to know what a lab can actually see and how a treatment program confirms someone is taking it as prescribed.
This post explains how naltrexone differs from opioids at the receptor level, why a routine opiate panel does not pick it up, how a treatment program or monitoring agency can order a specific naltrexone and 6 beta naltrexol test to confirm adherence, and how naltrexone compares with buprenorphine and methadone, two medications that behave very differently on a drug test panel.
Naltrexone is an antagonist, not an opioid
Opioids such as morphine, oxycodone, and fentanyl bind to opioid receptors and activate them. Naltrexone binds to the same receptors but blocks them instead of activating them, which is why it is used to prevent relapse in opioid use disorder and to reduce cravings in alcohol use disorder. The Substance Abuse and Mental Health Services Administration describes naltrexone as a medication that blocks opioid receptors and is not itself an opioid and not a controlled substance, available as a daily tablet or as the monthly injectable formulation Vivitrol administered in a clinical setting. SAMHSA's naltrexone overview lays out both formulations and the conditions it is approved to treat. Because naltrexone does not activate opioid receptors and is structurally distinct from the morphine type compounds that opiate immunoassay strips target, it does not register as an opiate positive.
MedlinePlus, a National Library of Medicine consumer drug information resource, confirms naltrexone is dispensed by prescription, is not a controlled substance, and lists its approved uses for both alcohol dependence and opioid dependence, along with the warning that a person must be opioid free for a period before starting it to avoid precipitating withdrawal. MedlinePlus naltrexone drug information is a useful plain language reference for employees or family members trying to understand the medication itself, separate from any testing question.
Why the opiate immunoassay strip does not flag naltrexone
A standard five panel or ten panel cup includes an opiate (OPI) strip calibrated to morphine and codeine. It is not a generic opioid detector. Oxycodone, fentanyl, buprenorphine, and methadone each cross react poorly or not at all with the morphine calibrated OPI strip, which is why labs and test manufacturers offer separate OXY, FYL, BUP, and MTD strips for those specific drugs. The federal government's own testing framework for regulated workplace programs describes this analyte specific structure, where each screening immunoassay is built and calibrated around a defined target compound or drug class rather than a broad opioid category. The Mandatory Guidelines for Federal Workplace Drug Testing Programs, published by the Department of Health and Human Services, set the cutoff concentrations and target analytes that commercial immunoassay panels are modeled on.
Naltrexone is not morphine, not codeine, and not any of the analytes those panels are built around, so a standard immunoassay screen has no reason to cross react with it. There is no published evidence of naltrexone causing a false positive opiate screen, and because it is pharmacologically an antagonist rather than an opioid agonist, a positive result from naltrexone alone would run against the basic chemistry the immunoassay is measuring. Any claim beyond that, such as a specific cross reactivity percentage, is limited evidence and should not be treated as established.
How a treatment program confirms naltrexone adherence
A workplace drug test cup is not designed to look for naltrexone, so a treatment program, drug court, or monitoring board that wants to confirm a patient is actually taking naltrexone as prescribed has to order something different. Instead of an immunoassay screen, the lab runs a definitive liquid chromatography tandem mass spectrometry, or LC-MS/MS, test for naltrexone and its primary metabolite, 6 beta naltrexol. The Vivitrol prescribing information filed with the government describes naltrexone's metabolism to 6 beta naltrexol and the pharmacokinetic profile of both compounds, which is the basis labs use to design a confirmation test that proves recent dosing rather than simply screening for opioids. Vivitrol prescribing information on DailyMed is the authoritative label source for dosing, metabolism, and administration of the monthly injection.
This kind of adherence testing is ordered deliberately and specifically. It is not something that shows up as a byproduct of a routine pre employment or random workplace panel, and a general employer administered drug test cup will not report naltrexone or 6 beta naltrexol levels. Programs that need adherence confirmation typically coordinate directly with a laboratory capable of the LC-MS/MS method rather than relying on point of collection screening devices.
Naltrexone compared with buprenorphine and methadone
Naltrexone, buprenorphine, and methadone are all used in the treatment of opioid use disorder, but they behave very differently on a drug test panel, and conflating them leads to confusion for employers and for people in recovery.
| Medication | Drug class | Controlled substance status | Shows on standard opiate (OPI) strip | Dedicated strip needed |
|---|---|---|---|---|
| Naltrexone | Opioid antagonist | Not a controlled substance | No | No standard strip; LC-MS/MS used only for specific adherence testing |
| Buprenorphine | Partial opioid agonist | Schedule III | No, requires its own BUP strip | Yes, dedicated buprenorphine strip |
| Methadone | Full opioid agonist | Schedule II | No, requires its own MTD strip | Yes, dedicated methadone strip |
Buprenorphine, often prescribed as Suboxone, and methadone are both controlled substances that will appear on a drug test, but only on their own dedicated strips, not on the general opiate strip. A more detailed breakdown of buprenorphine panel design is available in our post on Suboxone and buprenorphine drug test panels, and the methadone specific testing approach is covered in our post on the methadone MTD panel. Naltrexone sits in a different category entirely because it blocks receptors instead of occupying them the way an agonist does, and it carries no federal scheduling.
The MRO process and why treatment medication is private
Whenever a laboratory based drug test returns a positive screening result, a certified medical review officer reviews the result before it is reported to an employer. The MRO contacts the employee, reviews any current prescriptions, and determines whether a legitimate medical explanation accounts for the result. Because naltrexone does not cause a positive opiate screen in the first place, an employee taking it generally has nothing to explain through the MRO process on that basis. If an employer or program does order a specific naltrexone confirmation test for a legitimate clinical or monitoring reason, that result is still handled through the same confidential medical review channel, not reported as a raw lab value to a supervisor or HR contact.
Our post on the medical review officer process walks through how MRO review works step by step, including how prescription documentation is verified and kept confidential. Treatment for alcohol or opioid use disorder is medical information, and it should be handled with the same discretion as any other prescribed medication, documented through the proper verification channel rather than discussed informally at work.
Frequently asked questions
Does naltrexone cause a positive opiate drug test?
No. Naltrexone is an opioid antagonist, not an opioid, and standard opiate immunoassay strips are calibrated to morphine and codeine. There is no established evidence that naltrexone causes a false positive on a standard opiate panel.
Can a regular drug test cup detect Vivitrol?
A standard multi panel drug test cup used for pre employment or workplace screening is not designed to detect naltrexone or its metabolite, 6 beta naltrexol. Detecting those compounds requires a specific LC-MS/MS laboratory test ordered for adherence monitoring, not a point of collection immunoassay cup.
Is naltrexone a controlled substance?
No. Naltrexone is not scheduled as a controlled substance in the United States, unlike buprenorphine, which is Schedule III, and methadone, which is Schedule II.
How does a treatment program confirm someone is taking naltrexone?
Some treatment programs and monitoring agencies order a dedicated laboratory test for naltrexone and 6 beta naltrexol using liquid chromatography tandem mass spectrometry, which confirms recent dosing rather than relying on a standard opiate screen.
Will naltrexone show up differently than buprenorphine or methadone on a drug test?
Yes. Buprenorphine and methadone are opioid agonists and controlled substances that require their own dedicated test strips, separate from the general opiate strip. Naltrexone is an antagonist with no federal scheduling and is not part of a standard opioid panel at all.
Does taking naltrexone need to be disclosed during a workplace drug test?
Prescription medications are generally reviewed through the medical review officer process when a test result is positive and an explanation is needed. Since naltrexone does not typically cause a positive opiate result, there is usually nothing to explain, but documentation should still go through the confidential MRO channel rather than being shared informally.
Employers who want to review their own screening program should confirm which opioid specific strips their panel includes, since a standard opiate strip alone will not detect buprenorphine, methadone, or several other opioids. Our drug test cups collection includes multi panel configurations with dedicated strips for the specific opioids a program needs to screen for, rather than relying on the general opiate strip alone.
This article is general information for employers and individuals and is not legal or medical advice. Testing panels, scheduling status, and treatment program requirements vary, and anyone with questions about a specific result or program should consult a qualified medical review officer, treating clinician, or legal counsel.
