Vivitrol is a once-monthly injection that reduces the rewarding feeling alcohol produces in your brain. It contains naltrexone, a medication that blocks specific receptors in your nervous system so that drinking feels less pleasurable and the urge to keep drinking weakens over time. It doesn’t make you sick if you drink (that’s a different medication, disulfiram). Instead, it quietly takes the “high” out of alcohol, making it easier to cut back or stop.
What Happens in Your Brain
When you drink alcohol, your body releases its own natural opioid-like chemicals called endorphins. These endorphins latch onto opioid receptors in the brain, especially a type called mu opioid receptors, and trigger a wave of pleasure. Over time, your brain starts associating alcohol with that reward, reinforcing the cycle of craving and drinking.
Naltrexone, the active ingredient in Vivitrol, has the highest affinity for those same mu opioid receptors. It sits on the receptors and blocks endorphins from binding to them. With those receptors occupied, the cascade of pleasurable feelings you normally get from alcohol is significantly dulled. You might still feel some effects of alcohol (it still impairs coordination and judgment), but the reinforcing “buzz” or euphoria is muted. Scientists note that the full neurobiological picture isn’t entirely mapped out yet, but the core mechanism is this receptor blockade that disrupts alcohol’s reward signal.
The practical result: many people on Vivitrol describe being able to have a drink put in front of them and simply not caring about it the way they used to. The obsessive pull toward the next drink loosens because the payoff your brain expects never fully arrives.
How It’s Given
Vivitrol is delivered as a 380 mg intramuscular injection once every four weeks. A healthcare provider administers the shot into the gluteal muscle (the buttock), alternating sides each month. You cannot give it to yourself at home.
Because the medication is embedded in tiny microspheres that dissolve slowly, naltrexone releases steadily into your bloodstream over the full 28-day window. This is a major advantage over the oral pill form of naltrexone, which requires you to remember to take it every day. With Vivitrol, once the injection is done, the medication is working whether you think about it or not. That removes the daily decision point where someone struggling with cravings might skip a dose.
How Well It Works
In a real-world pilot program run by the Los Angeles County Department of Public Health, patients receiving Vivitrol alongside outpatient counseling reduced their substance use from an average of 11.7 days per month before treatment to just 1.3 days per month by the time they finished. Patients in residential treatment programs who received Vivitrol saw a similar drop, going from 13.8 days of use per month down to 0.9 days.
Importantly, people who received Vivitrol consistently fared better than those in the same treatment settings who did not get the injection. That suggests the medication adds a measurable benefit on top of counseling and structured support. Vivitrol is not a magic fix on its own. It works best as part of a broader plan that includes some form of therapy, whether that’s individual counseling, group support, or a structured recovery program.
What Treatment Looks Like Over Time
You’ll typically return to your provider every 28 days for a new injection and a check-in. During that visit, your provider assesses how you’re responding, whether you’re experiencing side effects, and whether you’re engaging in any additional support like counseling. Treatment length varies by person. Some protocols authorize up to 12 months of continuous therapy before requiring a formal review of whether to continue.
There’s no hard rule that says you must stop at 12 months. Some people stay on Vivitrol longer if they and their provider agree it’s helping. Others may taper off sooner if they’ve built strong coping strategies and feel stable. The key is that each monthly visit serves as a checkpoint, not just an injection appointment.
Before You Start
There are a few important requirements before that first shot. If you also use opioids (prescription painkillers, heroin, or anything similar), you need to be completely free of them for at least 7 to 10 days before receiving Vivitrol. Because the medication blocks opioid receptors, injecting it while opioids are still in your system can trigger sudden and severe withdrawal symptoms.
Liver health is another consideration. Naltrexone is processed by the liver, and high doses have been associated with liver stress in some cases. Your provider will likely check liver function with a blood test before starting treatment and may monitor it periodically. If you have existing liver disease, that doesn’t automatically disqualify you, but it’s something your provider needs to factor in.
Common Side Effects
The most frequently reported issue is a reaction at the injection site: soreness, a hard lump, redness, or tenderness in the buttock where the shot was given. This usually fades within a few days but can occasionally be more pronounced. Nausea is another common early side effect, particularly after the first injection, and it tends to lessen with subsequent doses. Some people also report headaches, fatigue, or dizziness in the first week or two.
Because Vivitrol blocks opioid receptors, it also blocks the effects of opioid pain medications. If you need surgery or emergency pain treatment while on Vivitrol, your medical team needs to know you’re taking it so they can use alternative approaches for pain management. Carrying a card or wearing an alert that notes you’re on naltrexone is a practical precaution.
How Vivitrol Differs From Other Medications
Three medications are FDA-approved for alcohol use disorder, and they work through completely different mechanisms. Disulfiram (Antabuse) makes you physically ill if you drink by blocking your body’s ability to process alcohol. It relies on fear of that reaction as a deterrent. Acamprosate works on a different brain chemical system entirely, helping to calm the restlessness and anxiety that come with early sobriety.
Vivitrol’s approach is distinct: it targets the reward pathway. It doesn’t punish you for drinking and it doesn’t calm withdrawal symptoms. It changes the equation by making alcohol less satisfying. For many people, that shift is enough to break the pattern of compulsive drinking, especially when paired with support that helps them build new habits in the space the medication creates.