How long does naltrexone stay in your system?
Alcohol Use Disorder
The pill clears your blood in about 1 to 2 days. A single 50 mg dose blocks opioids for around 24 hours.
How long it lasts
Timelines for the pill and the monthly Vivitrol shot
Drug class
Opioid antagonist
Half-life (pill)
About 4 hours
Active byproduct
About 13 hours
Clears your blood
About 1 to 2 days
Blocks opioids (50 mg)
About 24 hours
Vivitrol shot lasts
About 1 month
Opioids work again
1 to 3 days after pill
Shows on a drug test?
No
Naltrexone is not an opioid, so it does not show on standard drug tests.
1 to 2 days
for the oral pill to mostly clear from your blood
24 hours
one 50 mg pill blocks opioids for about a day
1 month
the Vivitrol injection keeps working per single shot
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.
Looking for naltrexone by telehealth? See our naltrexone online service page.
Naltrexone treatment is coming to Recovery Delivered
See a provider by video, or handle everything by secure message. Your choice, same care, medication mailed to your door. Join the waitlist to be first in line when we open.
No spam. We will only email you about naltrexone for alcohol at Recovery Delivered.
Frequently asked questions
How long does naltrexone stay in your system?
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?
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?
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?
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.
- 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.