Vivitrol injection (naltrexone): Side effects, dosage, and more

If you’ve ever wished there were a button that could mute alcohol or opioid cravings,
Vivitrol might feel a little bit like that. It’s not magic, and it’s definitely not a cure,
but this monthly injection of extended-release naltrexone can be a powerful tool in recovery
when used with counseling and other support. In this guide, we’ll walk through what Vivitrol is,
how it works, typical dosing, potential side effects, and what real people often experience when
they start treatment.

What is Vivitrol?

Vivitrol is the brand name for an extended-release injectable form of
naltrexone, a medication called an opioid antagonist. That means it
attaches to opioid receptors in the brain and blocks them instead of activating them.
In doing so, it helps reduce the rewarding “high” or buzz from alcohol and opioids.

Unlike oral naltrexone pills that you take once a day, Vivitrol is given as a
once-monthly intramuscular injection into the gluteal (buttock) muscle.
The medication is released slowly over about four weeks, helping people avoid the
“I forgot my pill” problem that can limit the effectiveness of daily medications.

What is Vivitrol used for?

In adults, Vivitrol is approved to:

• Treat alcohol dependence in people who have already stopped drinking before the first injection.
• Prevent relapse to opioid dependence after a person has gone through opioid detox and is completely opioid-free.

It’s important to stress that Vivitrol is not a stand-alone cure. It’s meant to be used
as part of a comprehensive program that may include individual or group counseling,
behavioral therapies, peer support, and social services. Medication plus support generally
gives better long-term outcomes than either approach alone.

How Vivitrol works in your body

Vivitrol’s active ingredient, naltrexone, works by blocking opioid receptors,
specifically the mu-opioid receptors involved in pleasure, reward, and pain. For people with:

• Alcohol use disorder (AUD): Blocking these receptors can reduce the pleasurable effects of drinking and help decrease cravings and heavy drinking days.
• Opioid use disorder (OUD): Naltrexone blocks the effect of opioids like heroin, oxycodone, or fentanyl. If someone on Vivitrol uses opioids, they’re much less likely to feel the usual high.

After injection, the medication is gradually released from tiny microspheres in the muscle,
providing a long, steady exposure rather than a quick spike and drop. This extended-release
design is what allows Vivitrol to be dosed about once every four weeks.

Who might be a good candidate for Vivitrol?

Vivitrol is generally considered for adults who:

• Have a diagnosed alcohol use disorder or opioid use disorder.
• Have already stopped drinking or using opioids and want extra support to stay that way.
• Can attend regular appointments to receive monthly injections.
• Do not have certain medical conditions that make naltrexone unsafe, such as severe hepatitis or liver failure.

Your healthcare provider will usually review your medical history, check your liver function tests,
and go through your current medications before deciding if Vivitrol is appropriate. It’s not
recommended for people who are currently using opioids, in acute withdrawal, or have a positive
opioid screening test.

Very important: being opioid-free first

For people with opioid use disorder, starting Vivitrol too soon after using opioids can trigger
precipitated withdrawala sudden, intense withdrawal reaction that can feel much
worse than typical withdrawal. To reduce that risk, people generally must be opioid-free for
several days or longer (the exact timing depends on the opioid used and other factors) before
the first injection. Your provider may use a urine drug screen or a test dose of another
medication to make sure it’s safe to start.

Vivitrol dosage and how the injection is given

Standard Vivitrol dosage

The standard adult dose of Vivitrol is:

• 380 mg injected into the gluteal muscle once every 4 weeks (about every 28 days).

The injection is not self-administered. It must be given by a healthcare
professional who has been trained to mix the medication and inject it correctly into the muscle.
Injecting into the wrong location or too shallowly can increase the risk of serious injection
site problems.

Before your first Vivitrol shot

Before starting Vivitrol, your provider may:

• Confirm that you’ve stopped drinking (for AUD) or are fully off opioids (for OUD).
• Review your past and current medical conditions, including liver or kidney issues.
• Check your liver enzymes and other labs as needed.
• Discuss contraception and pregnancy plans if you can become pregnant.
• Explain what to expect from the injection and the first few days afterward.

In some cases, people might try a short course of oral naltrexone first to see how they tolerate
the medication before committing to a long-acting injection, but this is not always required.

What the injection visit is like

At the clinic, the medication is prepared from a powder and mixed with a liquid right before
injection. The injection is given deep into the upper outer buttock. You’ll typically stay in
the clinic briefly afterward to make sure you feel okay, then you can go about your day.
You’ll schedule the next shot for roughly 4 weeks later.

Common side effects of Vivitrol injection

Like all medications, Vivitrol can cause side effects. Not everyone will experience them,
and many are mild and temporary. Still, it’s helpful to know what might show up so you’re
not caught off guard.

Injection site reactions

The most frequently reported side effects involve the injection site. These can include:

• Pain or soreness in the buttock
• Redness or bruising
• Swelling or firmness under the skin
• Itching or mild irritation

Mild discomfort for a few days is common and usually manageable with over-the-counter pain
relief (if approved by your provider), gentle movement, and avoiding pressure on the area.
However, severe, worsening, or unusual injection site symptomssuch as a hard lump that keeps
growing, skin turning dark, warmth, or an open woundneed prompt medical attention.

Other common side effects

People receiving Vivitrol sometimes report:

• Nausea or vomiting
• Headache
• Dizziness or lightheadedness
• Fatigue or low energy
• Loss of appetite
• Joint or muscle aches
• Sleep changes (insomnia or feeling unusually sleepy)
• Cold-like symptoms (runny nose, sore throat)

These effects are often mild and tend to improve as your body adjusts over the first few
injections. If a side effect is persistent, bothersome, or worsening, it’s worth discussing
with your healthcare provider. Sometimes adjusting timing, supportive treatments, or even
switching medications may be needed.

Serious side effects and warnings

While uncommon, serious side effects can occur. Contact your healthcare provider right away
or seek emergency help if you experience any of the following.

Severe injection site reactions

Rarely, Vivitrol injections have led to severe tissue damage at the injection site that required
surgery. Warning signs include:

• Severe or increasing pain at the injection site
• Large areas of swelling, hardness, or a growing lump
• Blistering, an open wound, or a dark scab
• Fever or feeling very ill along with local symptoms

Precipitated opioid withdrawal

If Vivitrol is given to someone who still has opioids in their system, it can abruptly displace
those opioids from the receptors and trigger intense withdrawal. Symptoms may include:

• Severe nausea, vomiting, or diarrhea
• Stomach cramps
• Muscle aches and shaking
• Rapid heart rate, sweating, anxiety, or restlessness

This is one of the main reasons your provider will insist on a clean, opioid-free period before
your first injection.

Liver problems

Naltrexone, especially at high doses or in people with existing liver disease, can affect the liver.
Signs of possible liver injury include:

• Unusual fatigue or weakness
• Loss of appetite that doesn’t go away
• Right upper abdominal pain or tenderness
• Dark urine
• Yellowing of the skin or eyes (jaundice)

If you notice these symptoms, contact your provider promptly. They may order blood tests to check
your liver function and decide whether to continue treatment.

Allergic reactions

Serious allergic reactions are rare but possible. Get emergency help if you develop:

• Hives or widespread rash
• Swelling of the face, tongue, or throat
• Trouble breathing
• Severe dizziness or fainting

Overdose risk if you return to opioids

One of the less obvious but very important risks is what happens if someone on Vivitrol decides
to “test” the blockade or resumes opioid use after an injection wears off. Because Vivitrol blocks
opioid effects for a time, some people are tempted to take more opioids than usual to try to feel
a high. That can lead to an overdose, including potentially fatal respiratory depression.

Also, after a period of not using opioids, your tolerance drops. If you go back to your prior
“usual” dose, it may now be dangerously high. This is why counseling, overdose education, and
access to naloxone (an opioid overdose reversal medication) are crucial parts of care.

Drug interactions and precautions

Before starting Vivitrol, give your healthcare provider a complete list of everything you take, including:

• Prescription medications
• Over-the-counter drugs (especially those that might contain opioids, like some cough medicines)
• Vitamins, herbal supplements, and natural remedies

Key points to keep in mind:

• Opioid medications: Vivitrol blocks their effect, so pain medicines that rely on opioids may not work as expected. If you ever need surgery or emergency care, make sure the team knows you’re on Vivitrol.
• Other liver-affecting drugs: Combining multiple medications that stress the liver may require closer monitoring.
• Pregnancy and breastfeeding: Data are limited. If you’re pregnant, planning pregnancy, or breastfeeding, discuss risks and benefits carefully with your provider.

Vivitrol vs. other treatment options

For opioid use disorder, there are three FDA-approved medications:
methadone, buprenorphine (often combined with naloxone),
and naltrexone (including Vivitrol). Each has pros and cons.

• Methadone: A full opioid agonist taken once daily at a clinic. Very effective but highly regulated.
• Buprenorphine: A partial agonist, often taken as a sublingual pill or film. Can be prescribed in office-based settings.
• Vivitrol (naltrexone): A blocker, given monthly. Requires that you be fully detoxed and opioid-free before starting.

For alcohol use disorder, options include oral naltrexone,
extended-release injectable naltrexone (Vivitrol),
acamprosate, and disulfiram. The “best” choice depends on
your medical history, your pattern of use, your preferences, and practical issues such as cost,
insurance coverage, and access to services.

Everyday life on Vivitrol: what to expect

For many people, the biggest changes with Vivitrol are:

• Fewer cravings: The urge to drink or use may not disappear, but it often softens enough to give you room to make different choices.
• More predictable days: Instead of thinking about taking a daily pill, you simply plan around a monthly visit.
• Opportunities to focus on recovery: With cravings turned down, therapy, work on relationships, and life goals become slightly more manageable.

However, it’s normal to still experience stress, emotional triggers, and old habits. Medication is
one toolyour support network, coping skills, and environment still matter a lot.

Real-world experiences with Vivitrol: Side effects, dosage, and more

While everyone’s story is different, there are some common themes people describe when talking about
their experiences with Vivitrol injections.

Adjusting to the first few injections

Many people say the first injection is the most anxiety-provoking, simply because it’s new. You might
be wondering: “Will it hurt? Will I feel weird right away? What if it doesn’t work?” Typically, the
injection feels like a firm, deep shotuncomfortable but brief. Soreness over the next day or so is
common, especially if you sit a lot or sleep on that side.

In the first one to two weeks, some people report nausea, headaches, or fatigue. Others feel a bit
“off” or emotionally flat as their brain adjusts to the loss of alcohol or opioid effects. This may
be partly medication-related and partly about the big change in your body’s reward system. For many,
these sensations ease by the second or third injection.

Cravings and “testing the blockade”

A frequent experience is noticing that cravings become less sharp and less constant. Instead of being
pulled toward a drink or pill all day, you might notice thoughts about using pop up and then pass more
easily. That doesn’t mean cravings vanish, but they become more manageablelike background noise rather
than a blaring alarm.

Some people are curious and consider “testing” whether Vivitrol really blocks opioids or blunts
alcohol’s effects. Healthcare providers strongly warn against this. Trying to override the blockade
can lead to overdose or serious harm. If you find yourself thinking about testing it, that’s a
good time to reach out to your counselor or support group and talk through those urges.

The monthly rhythm of treatment

A monthly injection creates a built-in rhythm: you know that once every four weeks, you’ll be seeing
your provider. Many people find this reassuringit becomes a regular check-in point to talk about how
things are going, adjust other medications, or address life stressors.

Some people plan their injections around paydays, major events, or busy seasons at work. Others like
to keep visits at the same time and day every month to build consistency. It can help to plan a lighter
day after your injection if you know you tend to feel sore or fatigued.

Managing side effects in everyday life

When side effects do appear, people often manage them with simple strategies:

• Using approved over-the-counter pain relievers for injection site soreness (if cleared by their provider).
• Applying gentle movement and stretching rather than staying completely still.
• Staying hydrated and eating small, frequent meals if nausea is an issue.
• Prioritizing sleep, especially during the first few days after an injection.

Communication with the clinic is key. If something feels “not normal,” most providers would rather
hear from you early than late.

Emotional and social changes

Emotionally, people can experience a wide range of reactions. Some feel hopeful and empowered:
“I finally have a medication backing me up.” Others feel a little anxious about losing their old
coping mechanism, even if that coping mechanism was harmful.

Socially, you might notice shifts too. Friends or family might react differently when they learn
you’re on a medication for alcohol or opioid use disordersome will be supportive, some may not
understand, and a few might feel threatened if they’re still using. Having a therapist, peer support
group, or trusted friend who “gets it” can make a huge difference.

Sticking with itand stopping

Many people stay on Vivitrol for several months to a year or more, depending on their recovery plan.
Over time, as life stabilizes, they might decide with their healthcare provider to stop injections,
switch to another medication, or rely more on behavioral supports alone.

When people stop, they usually don’t feel a dramatic withdrawal from Vivitrol itself. However, the
protection it offers fades over time. That’s when relapse prevention skills, strong support systems,
and realistic expectations become especially important. Some people choose to keep naloxone at home
and educate loved ones about overdose risks even after finishing medication treatment.

The bottom line

Vivitrol (naltrexone) injection is a long-acting medication that can help reduce cravings, prevent
relapse, and support recovery from alcohol and opioid use disorders. It’s given once a month by a
healthcare professional and is designed to be used alongside counseling and other supportsnot as
a stand-alone cure.

Like any medication, it carries potential side effects and serious risks, including liver problems,
injection site reactions, and overdose risk if opioids are used on top of or after treatment. But for
many people, the trade-off is worthwhile: fewer cravings, more stability, and a bit more breathing
room to build a life that isn’t centered around alcohol or opioids.

If you think Vivitrol might be an option for you or someone you care about, the next step is a
detailed conversation with a healthcare provider who understands substance use disorders. They can
review your medical history, discuss risks and benefits, and help you decide whether this once-monthly
injection fits into your larger recovery plan.

Disclaimer: This article is for informational and educational purposes only and is not a substitute
for professional medical advice, diagnosis, or treatment. Always talk with a qualified healthcare
provider about your specific situation and before starting or stopping any medication.

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