Learn the common signs of mental illness in adults and adolescents.
Learn more about common mental health conditions that affect millions.
Find Your Local NAMI
Call the NAMI Helpline at
Or text "HelpLine" to 62640
Generic name: naltrexone (nal TREKS one)
All FDA black box warnings are at the end of this fact sheet. Please review before taking this medication.
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.
Naltrexone is a medication that works in the brain to treat dependence on alcohol or opioids. Naltrexone 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:
Do not stop taking naltrexone, even when you feel better. With input from you, your health care provider will assess how long you will need to take the medicine.
Missing doses of naltrexone may increase your risk for relapse.
You must be free of all opioid-containing substances (such as 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.
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 medicines will not work. Other types of pain medications (such as ibuprofen, naproxen, or acetaminophen) are not affected.
If you are planning on becoming pregnant, notify your healthcare 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. It is likely that 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, as it is likely that naltrexone crosses into the breast milk. The effects of naltrexone on the baby are unknown.
Naltrexone is available as an oral tablet and an intramuscular injection. Only your healthcare 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. 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 a friend to remind you or check in with you to be sure you are taking your medication.
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.
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.
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.
Evzio® (naloxone) nasal spray can be used to reverse overdose from opioids including methadone. 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.
Common side effects
Rare/serious side effects
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.
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 healthcare providers about all of the medications you are taking.
Naltrexone will begin working shortly after taking one dose.
There are no FDA black box warnings for naltrexone.
©2020 The College of Psychiatric and Neurologic Pharmacists (CPNP). CPNP makes this document available under the Creative Commons Attribution-No Derivatives 4.0 International License. Last Updated: January 2016.
This information is being provided as a community outreach effort of the College of Psychiatric and Neurologic 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 College of Psychiatric and Neurologic Pharmacists disclaims any and all liability alleged as a result of the information provided herein.
In a crisis? Call or text 988.