Extended-release injectable naltrexone, sold under the brand name Vivitrol, is an FDA-approved once-monthly shot specifically designed to help people with alcohol use disorder drink less. It is not a cure and it does not make alcohol physically impossible to consume, but it blunts the rewarding sensation that keeps heavy drinkers coming back. The evidence behind it is real, though more uneven than the marketing suggests, and a handful of newer injectable therapies in the research pipeline could eventually join it.
What the Shot Is and How It Works
Vivitrol is a long-acting formulation of naltrexone, a drug that blocks opioid receptors in the brain. Alcohol triggers the release of endorphins that bind to those same receptors, producing part of the pleasurable buzz that reinforces drinking. When naltrexone occupies those receptors first, the buzz is dulled. The drink still goes down, but the neurochemical payoff is muted, which over time can weaken the habit loop.
Naltrexone has been available as a daily oral pill since the mid-1990s. The injectable version, approved for alcohol use disorder in 2006, was developed to solve an obvious problem: people struggling with heavy drinking frequently forget or choose not to take a daily pill. A single intramuscular injection in a clinic delivers the drug in a slow-release polymer that maintains blood levels for roughly four weeks. That shifts the compliance burden from 30 daily decisions to one monthly appointment.
What the Evidence Shows
A systematic review of injectable naltrexone trials found that the medication consistently produced positive outcomes, including a longer stretch before the first drink or heavy drinking day, fewer drinking days overall, and increased abstinence, with many of these results reaching statistical significance in the larger studies.1PubMed. Efficacy of Extended-Release Injectable Naltrexone on Alcohol Use Disorder Treatment: A Systematic Review Earlier research specifically noted the shot’s efficacy at decreasing heavy drinking among alcohol-dependent men.2PubMed Central. Naltrexone long-acting formulation in the treatment of alcohol dependence
The picture gets more complicated when you look at a large 2024 meta-analysis that pooled results from multiple randomized trials. That analysis found injectable naltrexone was not significantly better than placebo at preventing a return to any drinking or a return to heavy drinking. Where it did help was in reducing the percentage of drinking days and heavy drinking days: roughly five fewer percentage points of drinking days and about five fewer percentage points of heavy drinking days compared to placebo.3JAMA. Pharmacotherapy for Alcohol Use Disorder: A Systematic Review and Meta-Analysis In plain terms, the shot does not reliably prevent people from picking up a drink at all, but it does help them drink less often and binge less when they do drink.
That distinction matters. If your goal is total abstinence and nothing else counts, the injectable may disappoint. If your goal is harm reduction — fewer heavy drinking nights, fewer blackouts, fewer emergency room visits — the evidence is more encouraging. A network meta-analysis that compared several medications head-to-head against placebo found that oral naltrexone reduced heavy drinking and that acamprosate was better at maintaining abstinence, while naltrexone had a larger effect on reducing heavy drinking and cravings.4PubMed Central. Meta-analysis of naltrexone and acamprosate for treating alcohol use disorders: When are these medications most helpful? The injectable form carries the same active drug and the same basic profile, just delivered differently.
How Injectable Compares to the Daily Pill
The intuitive case for the shot over the pill is that you cannot skip it once it is in your muscle. A trial comparing injectable versus oral naltrexone for opioid use disorder (not alcohol specifically, but the same medication and the same adherence logic) found that roughly 57% of patients in the injectable group stayed in treatment for six months, compared to about 28% in the oral group.5PubMed Central. A Randomized Trial Comparing Extended-Release Injectable Suspension and Oral Naltrexone, Both Combined With Behavioral Therapy, for the Treatment of Opioid Use Disorder Staying in treatment is half the battle.
But better adherence does not always translate into better drinking outcomes. A recent randomized trial of hospitalized patients with alcohol use disorder compared injectable and oral naltrexone directly. At three months, heavy drinking days dropped substantially in both groups, with no statistically significant difference between them. Healthcare utilization after discharge was also similar.6PubMed Central. Oral vs Extended-Release Injectable Naltrexone for Hospitalized Patients With Alcohol Use Disorder A Randomized Clinical Trial Another study focused on patients with both PTSD and alcohol use disorder found no differences in the probability of remission for either condition between injectable and oral naltrexone.7PubMed. Comparative Effectiveness of Long Acting Injectable Versus Oral Naltrexone in Patients with Co-Occurring Posttraumatic Stress Disorder and Alcohol Use Disorder
The takeaway is a little deflating for the injectable’s premium price tag: if you are the sort of person who will reliably take a daily pill, the shot may not add much. Its real advantage is for people who know they will not take a pill every day, or who have tried and failed oral naltrexone because of spotty compliance. The shot removes that variable entirely.
Side Effects and Safety
Most side effects of injectable naltrexone are mild or moderate. The commonly reported ones include cold-like symptoms, insomnia, elevated blood pressure, and pain at the injection site.8PubMed. Injectable Extended-Release Naltrexone to Treat Opioid Use Disorder In a small study of patients with advanced alcohol-associated liver disease, about 29% experienced mild adverse effects like injection site pain, nausea, fatigue, and sexual side effects, but none developed drug-induced liver damage or worsening liver function.9PubMed Central. Safety and Tolerability of Injectable Extended-Release Naltrexone for the Management of Alcohol Use Disorder in Advanced Alcohol-Associated Liver Disease
The liver concern is worth unpacking because it trips people up. Naltrexone’s prescribing label carries a warning about hepatotoxicity, which can scare clinicians away from prescribing it to the very patients who need it most — people with alcohol-related liver damage. The evidence so far suggests that injectable naltrexone does not significantly increase the rate of liver enzyme elevations compared to placebo, and that when elevations do occur, they tend to be transient and are mostly seen in patients who already have hepatitis C.10PubMed. Hepatic safety of injectable extended-release naltrexone in patients with chronic hepatitis C and HIV infection Still, monitoring liver function during treatment is standard practice.
The more dangerous risk involves opioids. Naltrexone blocks opioid receptors, so anyone who also uses opioids — whether prescribed or not — faces the possibility of precipitated withdrawal, which can be severe and, in the case of the long-acting injection, impossible to reverse quickly. One case report described a young man who developed agitation and altered mental status after receiving the injection at the end of a detox program during which he had secretly continued using heroin.11PubMed. Severe opioid withdrawal precipitated by Vivitrol® Clinics are supposed to confirm an adequate opioid-free period before administering the shot, but the recommended seven-to-ten-day opioid-free window is itself a problem: during that gap, patients are vulnerable to cravings and dropout.12JAMA Network Open. Rapid Initiation of Injection Naltrexone for Opioid Use Disorder: A Stepped-Wedge Cluster Randomized Clinical Trial Another risk on the other end of treatment: once the shot wears off, opioid tolerance is lower, and any return to opioid use carries a heightened overdose risk.
Why It Costs So Much and Who Pays
Vivitrol is expensive. Oral naltrexone is available as a cheap generic, often under a dollar a day. The injection costs over $900 a month at full price. For people on Medicare Part D without supplemental coverage, that price means they can hit their coverage gap in seven to eight months of treatment, at which point they become responsible for the full cost.13PubMed. Medicare prescription drug plan coverage of pharmacotherapies for opioid and alcohol dependence in WA Private insurance plans, Medicaid, and manufacturer assistance programs may cover some or all of the cost, but access varies widely by state and plan.
This creates a frustrating dynamic: the people who would benefit most from the injection’s built-in compliance — those with unstable housing, chaotic schedules, or a history of not following through with daily medication — are often the same people with the least reliable insurance coverage. Many addiction clinics and hospital programs have found ways to administer the first injection during an inpatient stay, which is often covered, but continuing monthly injections after discharge depends on the patient navigating insurance approval and scheduling follow-up appointments.
Why People Choose the Shot Over Other Options
Interviews with hospitalized patients who accepted injectable naltrexone reveal motivations that go beyond the clinical data. Most reported accepting the shot because they hoped it would improve their health and relationships, because a monthly visit was more convenient than a daily pill, and because the injection offered a sense of security that they could not simply stop taking it on a bad day.14PubMed Central. Perspectives of In-Hospital Intramuscular Naltrexone and Oral Medications for Alcohol Use Disorder: A Study of Addiction Clinicians and Hospitalized Patients That last point is psychologically revealing. For some people, the fact that the drug is already locked into their body for the next month provides a kind of external willpower that they do not trust themselves to supply. Clinicians working in addiction medicine describe patients who request the shot specifically because they know they will talk themselves out of the pill.
A pilot study of patients who received the injection before hospital discharge found that while overall readmission rates and emergency department visits did not change significantly, the average length of subsequent hospital stays was significantly shorter.15The Primary Care Companion for CNS Disorders. Impact of Hospital-Administered Extended-Release Naltrexone on Readmission Rates in Patients With Alcohol Use Disorder: A Pilot Study That suggests the shot may not prevent future crises entirely but may reduce their severity, which lines up with the broader evidence that naltrexone moderates drinking rather than eliminating it.
Genetics and Who Responds Best
Not everyone responds to naltrexone equally, and researchers have spent years trying to figure out who benefits most. Much of the attention has focused on a gene called OPRM1, which codes for the mu-opioid receptor that naltrexone targets. A variant of this gene (sometimes called the Asp40 or G allele) was identified in the large COMBINE trial as a strong predictor of naltrexone response: among people carrying that variant who received naltrexone, about 87% had a good clinical outcome, compared to roughly 55% of those without it.16Archives of General Psychiatry. An Evaluation of μ-Opioid Receptor (OPRM1) as a Predictor of Naltrexone Response in the Treatment of Alcohol Dependence
However, the story is messier than one gene test deciding who gets the shot. A more recent study of extended-release injectable naltrexone found the opposite pattern: the A/A genotype (meaning no copies of the G variant) was associated with longer abstinence, lower relapse rates, and higher treatment completion. In that study, carrying the G allele actually increased relapse risk nearly threefold.17PubMed Central. OPRM1 rs1799971 Polymorphism Predicts Differential Response to Extended-Release Naltrexone in Alcohol Use Disorder: The Interplay of Genetics and Motivation Another crossover trial found that naltrexone’s effect on heavy drinking depended on interactions between OPRM1 and additional genes involved in dopamine signaling, with certain two-gene combinations predicting a strong response and others predicting little benefit.18PubMed Central. Opioid and Dopamine Genes Interact to Predict Naltrexone Response in Crossover Alcohol Use Disorder Clinical Trial
In practice, this means genetic testing for naltrexone response is not yet reliable enough to guide prescribing decisions in a clear-cut way. The field has been chasing a pharmacogenomic test for naltrexone for over a decade, and the data keep pulling in different directions depending on the study population, the outcome being measured, and which other genes are in the mix. Clinicians generally prescribe based on clinical judgment, patient preference, and trial and error rather than genotype.
GLP-1 Drugs and Alcohol
The most buzzworthy development in this space has nothing to do with naltrexone. GLP-1 receptor agonists — the class of injectable medications that includes semaglutide (Ozempic, Wegovy) and liraglutide — were designed for diabetes and obesity, but patients and researchers noticed that people taking them often lost interest in alcohol. That anecdotal signal has now been tested more rigorously.
A randomized trial gave low-dose semaglutide or placebo to adults with alcohol use disorder. Semaglutide did not reduce the number of days people drank, but it did reduce how much they drank on days they chose to drink, cut weekly alcohol cravings, and predicted a greater reduction in heavy drinking over time compared to placebo.19PubMed Central. Once-Weekly Semaglutide in Adults With Alcohol Use Disorder: A Randomized Clinical Trial A pooled analysis drawing on randomized trials, population-based studies, and biomarker data found that GLP-1 medications were associated with reduced alcohol intake, lower relapse rates, fewer alcohol-related diagnoses and hospitalizations, and improvements in biological markers of heavy drinking. Neuroimaging studies even showed dampened brain reactivity to alcohol cues.20eClinicalMedicine. Is There a Shot to Stop Drinking?
This is genuinely exciting, but important caveats apply. The randomized trial was small and short-term. Most of the population-level data come from people who were prescribed GLP-1 drugs for diabetes or obesity, not for drinking, which introduces confounding variables. No GLP-1 drug is currently approved for alcohol use disorder, and prescribing one off-label for that purpose means insurance almost certainly will not cover it. Still, several larger trials are underway, and if the results hold up, semaglutide could become the first new class of medication for alcohol use disorder in decades.
Experimental Approaches Further Down the Road
Beyond approved medications and GLP-1 repurposing, a few research threads are worth knowing about, though none are close to a clinic near you.
FGF21 is a hormone produced by the liver that appears to naturally suppress alcohol intake. In mice, a daily injection of the human version of FGF21 reduced voluntary alcohol consumption by about 21%.21PubMed Central. FGF21, a liver hormone that inhibits alcohol intake in mice, increases in human circulation after acute alcohol ingestion and sustained binge drinking at Oktoberfest An analog of FGF21 cut alcohol intake by roughly half in both mice and alcohol-preferring primates without affecting water consumption or body weight.22Cell Metabolism. Liver-derived FGF21 maintains alcohol consumption behaviors through the basolateral amygdala The primate data are encouraging because they suggest the effect is not limited to rodent biology, but clinical trials in humans have not yet been reported.
Gene therapy is the most radical concept being tested. Researchers delivered a gene for GDNF, a growth factor that supports dopamine neurons, directly into the brains of rhesus monkeys that had been trained to drink heavily. Over 12 months of repeated cycles where the monkeys had access to alcohol, the treated animals essentially stopped returning to heavy drinking.23PubMed Central. GDNF gene therapy for alcohol use disorder in male non-human primates The approach appeared to reverse the blunted dopamine signaling that chronic alcohol exposure causes, addressing a root-level neurological change rather than just blocking a receptor. This is a proof of concept in four monkeys, not a treatment anyone can receive, but it illustrates how far beyond “blocking the buzz” future approaches might reach.
Another frontier involves the brain’s immune signaling. Chronic alcohol exposure changes how immune-related molecules in the brain are regulated, contributing to neuroinflammation that perpetuates the cycle of dependence.24PubMed Central. Neuroimmune signaling in alcohol use disorder Targeting that immune pathway is a genuinely different angle from blocking opioid receptors or modulating appetite hormones, and early-stage drug development is exploring anti-inflammatory compounds as potential treatments. Whether any of these approaches will produce a viable injectable medication is unknown, but the variety of biological targets under investigation makes this a more active area of research than it was even five years ago.
Where Other Approved Medications Fit In
Naltrexone’s injectable form is not the only pharmacotherapy for alcohol use disorder, and understanding where it sits among the options helps you have a more productive conversation with a prescriber. A broad network meta-analysis found that several medications outperformed placebo for achieving total abstinence, with disulfiram, baclofen, gabapentin, and acamprosate all showing larger effect sizes than oral naltrexone for that particular outcome. For reducing heavy drinking specifically, disulfiram had the strongest signal, followed by baclofen, acamprosate, and oral naltrexone.25PubMed Central. Pharmacotherapies for Adults With Alcohol Use Disorders: A Systematic Review and Network Meta-Analysis None of these alternatives currently come in a long-acting injectable form approved for alcohol use disorder, though researchers are exploring sustained-release implants and other novel delivery systems for various addiction medications.
Disulfiram (Antabuse) works on a completely different principle: it makes you physically ill if you drink. Acamprosate stabilizes brain chemistry during early abstinence and helps people who have already stopped drinking stay stopped. Neither is a shot, both are daily oral medications, and each has its own side-effect profile and set of patients who do best with it. The point is that the injectable naltrexone shot is one tool among several, and the best choice depends on whether your primary goal is abstinence or reduced drinking, whether you are also managing other conditions, and whether you realistically will or will not take a daily pill.