Vivitrol is a 380 mg injection given into the gluteal (buttock) muscle once every four weeks. It cannot be self-administered at home. Each dose must be given by a healthcare professional in a clinical setting, such as a doctor’s office, clinic, or treatment center. The medication contains naltrexone, an opioid antagonist, suspended in microspheres that release the drug slowly over the course of a month.
What the Injection Involves
Vivitrol comes as a kit containing a vial of powder (the microspheres holding the medication) and a separate vial of liquid diluent. Before the injection, the provider mixes the two components together to create a suspension. This step has to be done correctly for the medication to work as intended, which is one reason the shot is restricted to clinical settings.
The injection goes into the upper outer quadrant of the buttock using a special needle included in the kit. It must be given intramuscularly, meaning deep into the muscle rather than under the skin or into a vein. Alternating sides each month is standard practice to reduce irritation at the injection site. The actual injection takes only a few seconds, though your appointment will likely last longer to allow for a brief check-in with your provider.
Requirements Before Your First Dose
If you are being treated for opioid dependence, you need to be completely opioid-free for a minimum of 7 to 10 days before receiving your first Vivitrol injection. This includes prescription opioids, heroin, and opioid-containing medications. The reason is straightforward: Vivitrol blocks opioid receptors, and if opioids are still attached to those receptors when the drug takes effect, it will force the body into sudden withdrawal. This “precipitated withdrawal” is far more intense than the discomfort of stopping opioids on your own and can be severe enough to require hospitalization.
Patients transitioning from longer-acting opioid medications like methadone or buprenorphine face a longer waiting period. These drugs clear the body more slowly, so the vulnerability to precipitated withdrawal can last as long as two weeks. Your provider will typically confirm you are opioid-free, sometimes with a urine test or a small test dose of oral naltrexone, before giving the injection.
For alcohol use disorder, there is no equivalent waiting period. You do not need to be abstinent from alcohol before starting Vivitrol, though many providers prefer to begin treatment after detoxification is complete.
What to Expect at the Injection Site
Some soreness, redness, or a small lump at the injection site is common and usually resolves on its own within a few days. Because the medication is a thick suspension delivered deep into muscle tissue, it can feel more uncomfortable than a typical shot. You may notice a firm nodule under the skin where the injection was given. This is the depot of microspheres slowly releasing medication, and it is normal.
In rare cases, more serious injection site reactions can occur, including significant pain that worsens over time, a large area of hardness or swelling, or skin changes like dark discoloration or open sores. These symptoms could indicate tissue damage and warrant prompt medical attention. Proper injection technique, specifically ensuring the needle reaches the muscle and avoids fatty tissue, significantly reduces this risk. This is another reason the shot must be given by a trained provider.
The Monthly Schedule
After your first dose, you return every four weeks for the next injection. Consistency matters because the microspheres are engineered to release naltrexone steadily over roughly 30 days. As you approach the end of that window, drug levels taper off, and protection decreases.
If you miss your scheduled appointment by a few days, you can generally receive your next injection without restarting any induction process. However, if a significant gap occurs, especially for opioid use disorder, your provider may need to reassess whether you have used opioids in the interim before giving another dose. The same 7-to-10-day opioid-free requirement applies any time there is a concern about recent opioid use.
Why an Injection Instead of a Pill
Naltrexone also exists as a daily oral tablet. The advantage of the monthly injection is that it removes the daily decision to take a pill. For people in recovery from opioid or alcohol dependence, adherence to a daily medication can be difficult, particularly during high-risk moments. With Vivitrol, one appointment per month provides continuous protection. Studies on medication adherence consistently show that long-acting injectable formulations result in more consistent drug levels and fewer gaps in treatment compared to daily oral versions of the same drug.
The tradeoff is that once the injection is given, it cannot be removed. If you experience side effects like nausea, fatigue, or headache, you will need to manage them for the duration of that month’s dose. This is something worth discussing with your provider before your first injection.
Where to Get Vivitrol
Vivitrol is available at addiction treatment centers, outpatient clinics, some primary care offices, and certain pharmacies that partner with prescribers. Because it requires intramuscular injection and proper reconstitution, you will always need an in-person visit. Some treatment programs include the injection as part of a broader recovery plan that also involves counseling or behavioral therapy. Insurance coverage, including Medicaid in most states, typically covers Vivitrol for both opioid and alcohol use disorder, though prior authorization requirements vary by plan.