Like any other drug, extended-release naltrexone (Vivitrol) can cause side effects in some people. The side effects from this medication, used to treat opioid and alcohol use disorder, usually are mild and don’t last long, but more serious reactions are possible.
It’s helpful to know how to manage the minor side effects and when to tell your doctor if you notice the more serious ones.
How to Manage Pain at the Spot Where You Got Your Naltrexone Shot
Since you’re given extended-release naltrexone as a shot, you may feel some pain and tenderness at the location of the shot, just as you would with a vaccine. This usually goes away within a few days.
In the meantime, you can ice the area for short periods throughout the day to help with any swelling and soreness. Move around, stretch a bit, and massage your muscles after the first 12 to 24 hours. If you’re still feeling uncomfortable, you can take an over-the-counter pain reliever like ibuprofen or acetaminophen.
To help prevent pain, relax your muscles when your doctor is giving you the shot.
You may notice a small lump at the shot location. This is common and should go away within 2 to 4 weeks.
Call your doctor if the skin becomes painful, red, and swollen and doesn’t get better within 1 week, or if you have a reaction that gets worse over time.
A serious skin reaction is possible, so tell your doctor right away if you have any of the following:
- Intense pain
- Hardness at the injection spot
- Blisters
- A large area of swelling
- An open wound
- A dark scab
How to Manage Other Common Side Effects of Naltrexone
Nausea and vomiting. You may feel nauseated after your first shot. This usually gets better within a few days, and it’s less likely to happen with future doses.
Take it easy while you’re feeling nauseated. Avoid strong odors like cooking, smoke, and perfumes. Try to avoid stuffy rooms, or heat and humidity if they make you feel worse.
Stay hydrated with small sips of cold, clear drinks like water, ginger ale, or mint tea. Eat bland foods like crackers and toast, then move on to cereal, rice, and fruit. Stay away from fatty or spicy foods. If you vomit, wait 6 hours before eating solid food.
Over-the-counter motion sickness medications can help if driving or riding in vehicles makes your nausea worse.
Headache. Rest and take pain medication like aspirin, ibuprofen, or naproxen to help with a mild headache.
Dizziness. If you feel dizzy, move slowly, especially when going from lying down to standing up. Drink plenty of fluids, but avoid caffeine and tobacco, as they can limit blood flow and make you more dizzy. Don’t drive or operate machinery until your dizziness gets better.
Sleepiness. If you’re feeling extra tired after starting on naltrexone, don’t drive or operate machinery. Feel free to take a short nap during the day, and also try to get some exercise, like a brisk walk.
Decreased appetite. Even if you’re not hungry, eat small meals at regular times. Choose foods high in protein, vitamins, and minerals to keep essential nutrients in your diet.
You could try liquid meals like smoothies, broth, or fruit juices if that makes it easier for you to get calories. Bland foods like unseasoned meat, dairy, potatoes, bread, and crackers might help if your stomach is feeling off.
You also may want to share meals with family and friends so you have support and encouragement to eat enough to stay healthy.
Joint pain or muscle cramps. For mild joint pain, you can take over-the-counter pain medications like ibuprofen or naproxen. Ice the joint for 15 to 20 minutes a few times a day. Ice can also help ease muscle cramps, as can stretching. A heating pad or warm bath or shower can soothe painful joints and muscles.
Cold symptoms. You may get a runny nose or other common cold symptoms after a naltrexone shot. To ease the discomfort, drink lots of liquids, use a humidifier in your room, and try a saline nasal rinse. Ask your doctor about treating your symptoms with over-the-counter pain medication or decongestant nasal spray.
What to Do if You Have Serious Side Effects From Naltrexone
Accidental opioid overdose. If you take a large amount of opioids to try to override the opioid-blocking effects of naltrexone, you could overdose. You also have a higher chance of overdosing if you use opioids around the time you are due for your next dose, if you miss a dose, or if you stop taking naltrexone. This is because your body will be more sensitive to opioids at that time.
Tell the people closest to you about this so they know to call 911 right away if they suspect you have used opioids and you:
- Have trouble breathing
- Become very drowsy with slowed breathing
- Have little chest movement with breathing
- Feel faint, very dizzy, or confused
Ask your doctor about naloxone, a medicine for the emergency treatment of an opioid overdose.
Sudden opioid withdrawal. If you have any opioids in your system at the time you get your first dose of naltrexone, you could feel sudden withdrawal symptoms. Go to the ER or see your doctor right away if your symptoms are severe.
Liver damage or hepatitis. Tell your doctor if you have any of these signs of liver damage or hepatitis while you are on naltrexone:
- Belly pain that lasts more than a few days
- Dark urine
- Yellowing of the whites of your eyes
- Tiredness
Depression. Be on the lookout for any signs of depression while you’re on naltrexone and call your doctor if:
- You feel sad or have crying spells.
- You lose interest in your friends or things you used to enjoy.
- Your sleep habits change a lot.
- You feel hopeless or helpless.
- You are more cranky, angry, or aggressive than usual.
- Your appetite or body weight changes.
- You have trouble paying attention.
- You feel tired or sleepy all the time.
- You have thoughts about hurting yourself or ending your life.
You can text or dial 988 to reach the 988 Suicide and Crisis Lifeline in an emergency. Your doctor can help put you in touch with mental health professionals such as psychiatrists and therapists who can treat your depression.
Pneumonia. An allergic reaction to naltrexone can cause a certain type of pneumonia. Tell your doctor right away if you have shortness of breath, wheezing, or coughing that doesn’t go away.
Serious allergic reactions. Get medical help right away if you have a severe skin rash, trouble breathing, wheezing, chest pain, dizziness, faintness, or swelling of your face, eyes, mouth, or tongue.
