How Long Does Naltrexone Stay in Your System?

Name: How Long Does Naltrexone Stay in Your System?
Creator: Recovery Delivered

The naltrexone pill clears from your blood in about 1 to 2 days, and a single 50 mg dose blocks opioids for around 24 hours. The Vivitrol injection is different: it works slowly and lasts about a month. Naltrexone is not an opioid, so it does not show up on standard drug tests.

Naltrexone comes in two forms, and how long each one lasts is very different. The daily pill leaves your body in a day or two, while the monthly injection is built to release slowly and stays in your body for weeks.

The daily pill

One 50 mg tablet a day. It clears your blood in about 1 to 2 days and blocks opioids for around 24 hours.

Clears in days

The monthly shot

The Vivitrol injection releases slowly, keeps working about four weeks, and can be found in the body for several weeks.

Lasts weeks

How long does naltrexone stay in your system?

For the pill, naltrexone itself has a half-life of about 4 hours, and its main active byproduct lasts about 13 hours. A half-life is the time it takes your body to clear half of a dose, and it takes several half-lives to clear a drug fully.

Oral naltrexone is mostly gone from your blood in about 1 to 2 days. Its opioid-blocking effect at the standard 50 mg dose lasts about 24 hours, which is why you take one pill a day.

How long does the Vivitrol injection last?

The Vivitrol injection is built to release naltrexone slowly over time. One 380 mg shot keeps working for about four weeks, which is why it is given monthly. Because it releases gradually, naltrexone from the injection can be found in the body for several weeks, tapering off toward the end of the month. This is by design, so you get steady coverage from a single monthly dose instead of a daily pill.

How long until opioids work again after naltrexone?

This matters if you ever need opioid pain relief. After your last naltrexone pill, the block fades over about 1 to 3 days as the medicine clears. After a Vivitrol injection, the block lasts much longer, and opioids may not work normally until around 28 days or more after the shot. If you have surgery or a painful injury planned, tell your care team you take naltrexone so they can plan non-opioid pain relief or time your dose.

Important: once naltrexone wears off, your body is more sensitive to opioids than it was before. Returning to a dose of opioids you once tolerated can cause a dangerous or fatal overdose. If you have used opioids in the past, talk with your provider before stopping naltrexone.

Does naltrexone show up on a drug test?

No. Naltrexone is not an opioid and is not included on standard drug-test panels, so it will not make you test positive for opioids or other drugs of abuse. It does the opposite of an opioid: it blocks those receptors. A special test could detect naltrexone if someone specifically looked for it, but routine workplace or medical drug screens do not check for it.

What affects how long naltrexone lasts?

A few things change the timeline. The form matters most: the pill clears in a day or two, while the monthly injection lasts weeks. The dose matters too, since higher doses block opioids a little longer. Your own body plays a role, including your metabolism and how well your liver and kidneys are working, because they process and clear the medicine. Even so, the general ranges above hold true for most people.

Naltrexone timeline at a glance

Here is how the common forms compare, from the standard daily tablet to the monthly injection.

Form	Blocks opioids for	Roughly clears the body in
50 mg tablet	About 24 hours	1 to 2 days
100 mg tablet	About 48 hours	2 to 3 days
Vivitrol injection (380 mg)	About 28 days	Several weeks

For related reading, see our naltrexone for alcohol guide, what to avoid, and side effects.

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Frequently asked questions

How long does naltrexone stay in your system?

The pill mostly clears your blood in about 1 to 2 days, and a 50 mg dose blocks opioids for around 24 hours. The Vivitrol injection works for about a month and can be found in the body for several weeks.

How long after naltrexone can you take an opioid?

After the pill, the block fades over about 1 to 3 days. After a Vivitrol injection, opioids may not work normally for around 28 days or more. Talk with your provider before using any opioid, and remember your tolerance is lower once it wears off.

Does naltrexone show up on a drug test?

No. Naltrexone is not an opioid and is not on standard drug-test panels, so it will not cause a positive result. Only a special test that specifically looks for naltrexone would detect it.

How long does the naltrexone shot last?

The Vivitrol injection lasts about four weeks per shot, which is why it is given once a month. It releases the medicine slowly, so its effect tapers toward the end of the month before the next dose.

Medically reviewed by

Daniel R. Karlin, MD, MA

Board-certified psychiatrist and addiction medicine specialist. Author of 21+ peer-reviewed publications (1,355 citations) including recent work in JAMA (2025) and the British Journal of Psychiatry (2023).

Google Scholar PubMed

Sources. U.S. Food and Drug Administration. Prescribing information for naltrexone (ReVia) and naltrexone extended-release injectable (Vivitrol), including pharmacokinetics and duration of opioid blockade.
Singh D, Saadabadi A. Naltrexone. StatPearls. National Library of Medicine (half-life of naltrexone and 6-beta-naltrexol).

This page is for education only and is not medical advice. Naltrexone is a prescription medication. Talk with a licensed provider about your specific situation.