Naltrexone (Vivitrol) | NAMI

Download PDF

Generic name: naltrexone (nal TREKS one)

  • Tablet: 50 mg

Brand names: Vivitrol®

  • Intramuscular injection: 380mg

All FDA black box warnings are at the end of this fact sheet. Please review before taking this medication.

Medication Assisted Treatment (MAT)

Medication assisted treatment (MAT) is the use of medications in combination with counseling and behavioral therapies for the treatment of substance use disorders. A combination of medication and behavioral therapies is effective in the treatment of substance use disorders and can help some people to sustain recovery.

What is naltrexone and what does it treat?

Naltrexone is a medication that works in the brain to treat alcohol or opioid use disorders. Naltrexone is an opioid antagonist which means it works by blocking the effect of opioid receptors and decreasing cravings and urges to use alcohol or opioids. This allows people who take the medication to control urges to use and help maintain abstinence from these substances. It is important to combine naltrexone treatment with counseling and other support.

Symptoms of alcohol and/or opioid dependence include:

  • Being unable to quit using alcohol or opioids despite problems with health and relationships.
  • Requiring more alcohol or opioids to achieve the same effect
  • Presence of withdrawal symptoms (sweating, shaking, nausea, vomiting, diarrhea, confusion, anxiety) when unable to use alcohol or opioids
  • Spending the majority of time using or finding a way to use alcohol or opioids
  • Having a desire but an inability to decrease the amount of alcohol or opioids used
  • Giving up enjoyable activities in order to use alcohol or opioids

What is the most important information I should know about naltrexone?

Do not stop taking naltrexone, even when you feel better. Only your health care provider can determine the length of treatment that is right for you.

Missing doses of naltrexone may increase your risk for relapse.

You must be free of all opioid-containing substances (such as tramadol, codeine, hydrocodone, oxycodone, morphine, or heroin) for at least 7 to 10 days before beginning naltrexone or you may experience withdrawal symptoms, such as sweating, shaking, nausea or vomiting. If you are on long-acting opioids (such as methadone), you may need to wait even longer for up to 14 days before beginning naltrexone.

After stopping naltrexone, you will respond to lower doses of opioids for pain. Do not begin using opioids at the doses you tolerated prior to starting naltrexone. Doing so puts you at risk for respiratory depression.

Liver injury may occur with naltrexone. This can be monitored through blood tests. Alert your doctor immediately if you experience any yellowing of your skin and/or eyes, severe stomach pain, or severe nausea or vomiting.

Patients with substance use disorders are at high risk for depression and suicidal thoughts. If you experience any thoughts of self-harm, call 911 or go to your closest emergency room.

Alert all of your physicians and pharmacists that you are taking naltrexone. Consider keeping a card in your wallet stating you are taking naltrexone to alert caregivers in case of emergency.

While on naltrexone, opioid pain medications will not work. Other types of pain medications (such as ibuprofen, naproxen, or acetaminophen) are not affected.

Are there specific concerns about naltrexone and pregnancy?

If you are planning on becoming pregnant, notify your health care provider to best manage your medications. People living with substance use disorders that wish to become pregnant face important decisions and challenges. Active substance use disorders during pregnancy put the fetus at great risk. It is important to discuss the risks and benefits of continued treatment with your doctor and caregivers.

The effects of naltrexone on the fetus when used in pregnant women are unknown. Naltrexone crosses the placenta and can be transferred to the fetus. Naltrexone did not appear to cause structural abnormalities during animal studies; however, there appeared to be some behavioral alterations as well as early fetal loss. These results cannot be applied to humans; therefore, naltrexone should only be used in pregnancy if the benefits outweigh the risk to the fetus.

Breastfeeding while taking naltrexone is not recommended because naltrexone crosses into the breast milk. The effects of naltrexone on the baby are unknown.

What should I discuss with my health care provider before taking naltrexone?

  • Symptoms of your condition that bother you the most
  • If you have allergies to any medications
  • If you have thoughts of suicide or harming yourself
  • Medications you have taken in the past for your condition, whether they were effective or caused any adverse effects
  • If you experience side effects from your medications. Some side effects may pass with time, but others may require changes in the medication.
  • Any other psychiatric or medical problems you have, including a history of liver or kidney disease
  • All other medications you are currently taking (including over the counter products, herbal and nutritional supplements) and any medication allergies you have
  • Other non-medication treatments you are receiving, such as talk therapy. Your provider can explain how these different treatments work with the medication
  • If you are pregnant, plan to become pregnant, or are breastfeeding
  • If you use illegal drugs or narcotics​

How should I take naltrexone?

Naltrexone is available as an oral tablet and an intramuscular injection. Only your health care provider can determine the route of administration and correct dose for you.

Naltrexone oral tablets are usually taken once daily with or without food. Taking naltrexone tablets with food may decrease stomach upset. Typically, people are given a test dose of 25 mg daily to ensure they can tolerate the medication. If the low dose is tolerated, the dose is increased to 50 mg daily.

The injection dose is 380 mg given intramuscularly every four weeks or once a month. These injections are given by your doctor, nurse, or pharmacist.

Consider using a calendar, pillbox, alarm clock, or cell phone alert to help you remember to take your medication. You may also ask a family member or friend to remind you or check in with you to be sure you are taking your medication.

What happens if I miss a dose of naltrexone?

If you miss a dose of oral naltrexone, take it as soon as you remember unless it is closer to the time of your next dose. Do not double your next dose or take more than what is prescribed.

What should I avoid while taking naltrexone?

Avoid drinking alcohol, using opioid pain medications (such as codeine, hydrocodone, oxycodone, or morphine), or using illegal drugs while you are taking naltrexone. They may increase adverse effects (e.g., sedation) of the medication.

Keep in mind that some cough syrups may contain opioid pain medication. Discuss all medications with your doctor and pharmacist prior to taking naltrexone.

What happens if I overdose with naltrexone?

If an overdose occurs, call your doctor or 911. You may need urgent medical care. You may also contact the poison control center at 1-800-222-1222.

Naloxone injection or nasal spray can be used to reverse an overdose from opioids. You should always call 911 after giving someone naloxone to treat an overdose. Ask your provider if prescription naloxone is right for you or your family member to have available.

What are the possible side effects of naltrexone?

Common side effects

  • Nausea, vomiting, headache, dizziness, muscle cramps, changes in appetite, anxiety, restlessness, or trouble sleeping (insomnia) may occur
  • Bruising, itching, tenderness, or swelling at the site of injection may occur with the injectable form of naltrexone

Rare/serious side effects

  • Increased blood pressure or heart rate, confusion, depression, nightmares, blurry vision, nasal congestion
  • Changes in liver function or liver failure
  • Suicidal thoughts have been reported. People experiencing suicidal thoughts while taking naltrexone should contact their provider immediately
  • Severe allergic pneumonia has been reported. Patients should contact their provider if they have symptoms of coughing, wheezing, or difficulty breathing

Are there any risks for taking naltrexone for long periods of time?

To date, there are no known problems associated with long term use of naltrexone. It is a safe and effective medication when used as directed.

What other medications may interact with naltrexone?

Naltrexone may decrease the effects of opioid medications, cough/cold medications, and certain anti-diarrheal medications. Do not take larger than recommended doses to achieve effects as this could lead to coma or death.

Avoid medications that may harm your liver, such as high doses of Tylenol® (acetaminophen). Talk to your health-care providers about all of the medications you are taking.

How long does it take for naltrexone to work?

Naltrexone will begin working shortly after taking one dose.

Summary of FDA Black Box Warnings

Naltrexone does not have any black box warnings.

Last Reviewed: January 2023

Provided by

This information is being provided as a community outreach effort of the American Association of Psychiatric Pharmacists. This information is for educational and informational purposes only and is not medical advice. This information contains a summary of important points and is not an exhaustive review of information about the medication. Always seek the advice of a physician or other qualified medical professional with any questions you may have regarding medications or medical conditions. Never delay seeking professional medical advice or disregard medical professional advice as a result of any information provided herein. The American Association of Psychiatric Neurologic Pharmacists disclaims any and all liability alleged as a result of the information provided herein.





©2022 American Association of Psychiatric Pharmacists (AAPP). AAPP makes this document available under the Creative Commons Attribution-No Derivatives 4.0 International License. Last Updated: January 2016.

NAMI HelpLine is available M-F, 10 a.m. – 10 p.m. ET. Call 800-950-6264,
text “helpline” to 62640, or chat online. In a crisis, call or text 988 (24/7).