How Does Vivitrol Work and How Long Does It Last

How Does Vivitrol Work

Here is the short version, because Vivitrol is simpler than the brand name makes it sound. Vivitrol is a once-monthly injection of extended-release naltrexone—it blocks opioids so they can’t get you high, and it dampens the reward of drinking, and one shot lasts about a month^[1].

That is the whole idea. It is not an opioid and it is not a substitute. It is a depot shot of the same opioid-blocking medicine that also comes as a daily pill, packed into a slow-release form so a single injection holds the block up for roughly four weeks. One decision a month instead of thirty.

So Vivitrol does for opioids and drinking what the pill does, by the same trick—it gets between you and the reward—but it takes the daily choice off the table. That is most of why it exists.

One thing covered below: how Vivitrol works, how long it lasts, and how it compares to the pill. For the full picture of the medicine, who it fits, and the side effects, start with the main Vivitrol guide.

What Vivitrol Is

Vivitrol is the brand name for the monthly injectable form of naltrexone, an opioid blocker. There is no new drug inside it. It is the exact same medicine as the daily naltrexone tablet, formulated as a long-acting shot so it releases slowly over weeks instead of clearing in a day^[1].

The form is what makes Vivitrol different, and the form is the point. Naltrexone the pill has to be swallowed every single day to keep working. Vivitrol is a depot injection—a shot given into the muscle of the buttock that parks a month’s worth of medicine in your body and lets it out gradually. A nurse or doctor gives it; you cannot inject it yourself.

Because it is naltrexone, Vivitrol carries the clean profile of the medicine: it isn’t an opioid, isn’t addictive, isn’t a controlled substance, and produces no high or withdrawal of its own. You don’t get euphoria from it and you can’t get hooked on it. That is why it can be handed out as a monthly shot rather than dispensed under watch at a clinic the way methadone is.

Is Vivitrol the Same as Naltrexone

Yes. Vivitrol is naltrexone—they are the same medicine, and the only real difference is how you take it.

Naltrexone comes in two forms. One is a daily pill you swallow. The other is Vivitrol, the monthly shot, which is naltrexone built into an extended-release form so a single injection lasts about four weeks. Same drug, same mechanism, same block on opioids and on the reward of drinking. The shot just trades the daily pill for a once-a-month visit^[1].

So when a provider says “naltrexone” they might mean either form, and when they say “Vivitrol” they specifically mean the injection. If you want the mechanism in full—how naltrexone sits on the opioid receptor and why it works on drinking too—see how naltrexone treats opioid addiction and drinking. Everything true of the pill’s mechanism is true of Vivitrol, because it is the same molecule.

The practical reason the shot exists is adherence. A daily pill only protects you on the days you actually take it, and the day a craving wins is exactly the day the pill gets skipped. Vivitrol removes that daily decision—one shot, and the block stays up whether or not your motivation does.

How Vivitrol Works

Vivitrol works by blocking the brain’s opioid receptors. Naltrexone is an opioid antagonist, which means it locks onto the same receptors that opioids need and sits there without switching them on. It occupies the seat so nothing else can sit down^[3].

That single action covers two problems at once:

• For opioids: with the receptor blocked, heroin, fentanyl, or a pain pill has nowhere to land. The high is muted or gone entirely. Strip the reward out and using stops being worth it—a slip becomes a dead end instead of a doorway back in^[3].
• For drinking: alcohol makes your brain release its own natural opioids, endorphins, and those endorphins hitting the reward system are a big part of what makes a drink feel good. Vivitrol sits on the receptor they would hit, so the pleasure and the pull are turned down.

The thing Vivitrol does not do is treat withdrawal. It is not an opioid and it gives no relief from being dope sick, which is why it is a second-stage medicine—you get clean first, then Vivitrol holds the line. For someone still in active withdrawal, an agonist that takes the agony off the table is the safer first step, and it helps to compare Suboxone and methadone.

How Long Vivitrol Lasts

One Vivitrol injection works for about four weeks, which is exactly why it is given once a month^[2].

The reason is the depot design. The naltrexone is suspended in tiny dissolvable microspheres, and after the shot they break down slowly in the muscle, releasing the medicine into the bloodstream a little at a time over the weeks that follow. The level rises in the first days, holds through the middle of the month, and then begins to taper toward the end. Across that stretch there is enough naltrexone on board to keep opioids blocked and the reward of drinking blunted^[2].

This is the practical strength of the shot. The daily pill asks for a fresh decision every morning. Vivitrol asks for one decision a month and then carries the block for you the rest of the time—through the bad days, the cravings, and the moments when motivation dips. For opioid recovery, where a single lapse can carry real overdose risk, that month-long coverage is the edge.

How Long Vivitrol Stays in Your System

Because the shot releases slowly, measurable naltrexone lingers in the body for several weeks after an injection—roughly the length of the dosing month, give or take, as the last of the microspheres dissolve and clear^[2].

That matters for one real reason: pain control. If you need surgery or land in an emergency room while Vivitrol is in your system, standard opioid painkillers may not work, because the block is still up. Tell every doctor, dentist, and surgeon that you are on Vivitrol so they can plan non-opioid pain control or adjust their approach. Unlike the daily pill—which you can simply stop a few days ahead of a planned procedure—a shot cannot be taken back once it is given, so this is a conversation to have before you ever need it.

What Happens as Vivitrol Wears Off

Near the end of the month, as the last of the medicine clears, the opioid block fades. This is the window that calls for the most care, and it is the most important safety point in Vivitrol treatment.

Here is the danger, said plainly. While Vivitrol is working and you are not using, your opioid tolerance drops. That is good—until the block wears off and someone goes back to the dose that used to feel normal. The body that once handled that dose no longer can, and today’s supply is often laced with fentanyl, which is far stronger and far less forgiving. The dose that felt routine a month ago can be the one that kills you^[1].

The point is not fear—it is the path. Vivitrol works best as an unbroken chain of monthly shots while the rest of recovery takes hold around it. A late or missed dose is a reason to call your provider, not a reason to use. And drinking carries the same logic: as the block fades, alcohol’s reward returns, so staying on schedule keeps the wall up. For the alcohol side of how this medicine works, see how naltrexone works for drinking.

Getting Help

If you are weighing Vivitrol, hold on to the simple version. It is the monthly shot form of naltrexone—an opioid blocker that lasts about a month per injection, so opioids stop getting you high and drinking stops feeling worth it, without a daily pill to remember. For a lot of people, that month-long wall is what finally makes staying clean feel doable instead of like a fight you have to win every single morning.

Vivitrol is one good option among several, and the right fit depends on where you are—still using, or already through detox and ready to hold the line. None of it is something you have to sort out alone. The way out is real, the medicine works, and the life on the other side is steadier than the fear talking you out of it. When you are ready, explore treatment centers and ask which medication fits you.

If you or someone you love is in danger right now, call or text 988 any time, or call 911 for a medical emergency.

Written by

Jessica Miller

Editorial Director

Jessica Miller is the Editorial Director of Addiction Help. Jessica graduated from the University of South Florida (USF) with an English degree and combines her writing expertise and passion for helping others to deliver reliable information to those impacted by addiction. Informed by her personal journey to recovery and support of loved ones in sobriety, Jessica's empathetic and authentic approach resonates deeply with the Addiction Help community.

Reviewed by

• Fact-Checked
• Editor

Kent S. Hoffman, D.O.

Co-Founder & Chief Medical Officer

Kent S. Hoffman, D.O. has been an expert in addiction medicine for more than 15 years. In addition to managing a successful family medical practice, Dr. Hoffman is board certified in addiction medicine by the American Osteopathic Academy of Addiction Medicine (AOAAM). Dr. Hoffman has successfully treated hundreds of patients battling addiction. Dr. Hoffman is the Co-Founder and Chief Medical Officer of AddictionHelp.com and ensures the website’s medical content and messaging quality.