• Addiction & recovery

Naltrexone Side Effects

Nzinga Harrison

July 14, 2021


Alcohol and opioid use disorders are two of the most prevalent forms of substance use disorders in the U.S. According to the National Institute on Drug Abuse (NIDA), approximately 50,000 people died from opioid-related overdoses in 2019. Opioid misuse and addiction, including prescription pain medications, heroin, and synthetic opioids like fentanyl, is a national epidemic that negatively impacts public health and social and economic welfare. 

According to the National Center for Biotechnology Information (NCBI), over 16 million people worldwide and  2.1 million people in the United States suffer from opioid use disorders (OUD). In 2019, around 14.5 million adults in the United States were diagnosed with an alcohol use disorder (AUD). 

Naltrexone is a prescription medication approved by the U.S. Food and Drug Administration (FDA) to treat alcohol and opioid use disorders. It has been in use for many years to help people in recovery avoid relapses and maintain abstinence by reducing cravings.

Naltrexone falls into the opioid antagonist (inhibitor) class of medications and is relatively pure and long-lasting. It is available in pill form (ReVia and Depade) for alcohol use disorder and an injectable form (Vivitrol) for alcohol and opioid use disorders. The pill form is prescribed daily to be taken at home or in a clinical setting, while the injectable form is administered once a month by a healthcare provider. The medication can be prescribed and administered by any healthcare practitioner licensed for dispensing medications. 


How Does Naltrexone Work?

Naltrexone, when used as part of alcohol addiction treatment, works by attaching itself to the endorphin receptors and blocking the effects and the “high” caused by alcohol. This function reduces an individual’s desire to drink and encourages them to remain in recovery. While naltrexone doesn’t stop you from drinking, it prevents you from achieving the intoxicating effects of alcohol.

When used as part of opioid maintenance treatment, naltrexone works by binding itself to the opioid receptors and blocking the euphoric effects of opioids. This reduces cravings and blocks the effects of any opioids during a relapse. Unlike methadone and buprenorphine, naltrexone does not activate opioid receptors. So the risk of misuse and diversion is relatively low when utilized in opioid maintenance treatment.

It’s worth noting that naltrexone is not a cure for alcoholism or opioid use disorder. While it may reduce the risk of relapses, it’s only effective when used in conjunction with a comprehensive treatment program that includes therapy, counseling, and an aftercare program. 


Who Is Most Suited for Naltrexone Treatment?

Even though naltrexone is considered an effective element in alcohol and opioid addiction treatment, it might not be a suitable treatment option for everyone. Hence, it’s important to seek the advice of a doctor before receiving naltrexone treatment. 

Naltrexone may be appropriate for individuals who are:

  • Aged 18 years and older.
  • Have been free of opioids for the past 7-14 days. 
  • Have successfully detoxed from alcohol and opioids. 
  • Have no existing liver conditions, kidney disease, or bleeding problems such as hemophilia.
  • Have no allergic reactions to naltrexone. 
  • Have not been receiving opioid analgesics for health conditions. 


Common Side Effects of Naltrexone 

As with any medications, naltrexone can also cause certain side effects that can be uncomfortable. Most of such side effects tend to be mild and disappear over time. 

Some of the most common side effects of naltrexone are: 

  • Diarrhea
  • Headache
  • Nervousness 
  • Sleeping troubles 
  • Muscle or joint pain
  • Nausea
  • Vomiting 
  • Loss of appetite
  • Constipation 
  • Dizziness 
  • Irritability
  • Enhanced or decreased energy 
  • Toothache
  • Cold symptoms 
  • Abdominal pain

If the side effects persist or worsens, it’s important to talk to your healthcare provider before discontinuing its use. Your physician can address the issue by adjusting your dosage or implementing an alternative medication. 

Naltrexone Side Effects - Eleanor Health

Severe Side Effects of Naltrexone 

Although not very common, naltrexone can cause severe side effects for certain individuals that may require immediate medical attention. Severe side effects of naltrexone may include:

  • Cellulitis
  • Induration
  • Hematoma
  • Abscess
  • Sterile abscess
  • Necrosis
  • Ringing in the ears
  • Blurred vision
  • Hallucinations
  • Pneumonia
  • Liver disease or hepatitis
  • Severe depression, which can lead to suicidal thoughts and behaviors 
  • Serious allergic reactions such as skin rash, wheezing, and chest pain 

Another possible side effect of the injectable form of naltrexone (Vivitrol) is injection site reactions. Injection site reactions after receiving Vivitrol treatment includes  symptoms such as:

  • Intense pain 
  • Swelling 
  • Lumps at the injection site 

Most of such reactions are mild and dissipate on their own. However, certain reactions, such as tissue death, may require surgery. Individuals receiving Vivitrol treatment should inform their healthcare practitioner if the symptoms at injection sites worsen over time or do not get better within two weeks. 


Other Risks of Naltrexone Treatment 

In addition to the risk of side effects, naltrexone can cause a condition known as Sudden Opioid Withdrawal Syndrome (SOWS). This condition is caused when naltrexone is used while opioids are still in your system. 

Since naltrexone attaches itself to the brain receptors and blocks the effects of opioids almost immediately, taking it when there are traces of opioids in the system can trigger a sudden opioid withdrawal. Sudden opioid withdrawal can be more severe than normal opiate withdrawal and include symptoms such as: 


  • Agitation 
  • Anxiety
  • Muscle aches
  • Teary eyes
  • Insomnia 
  • Sweating 
  • Yawning 
  • Diarrhea
  • Cramping 
  • Goosebumps 
  • Dilated pupils 
  • Nausea
  • Vomiting 

Individuals are advised to wait for at least seven days since the last use of short-acting opioids and 10-14 days for long-acting opioids before receiving naltrexone treatment. Individuals must also provide their physician with a list of all prescription, herbal, and over-the-counter medications currently in use as they may contain opioids.


Naltrexone Overdose

It’s theoretically possible to overdose on naltrexone. According to the Substance Abuse and Mental Health Services Administration (SAMHSA), individuals can experience an overdose during a relapse. After a period of abstinence, the decrease in tolerance levels can cause an accidental overdose when individuals consume the same dosage as before treatment.

Individuals can also experience an overdose if they take a large number of opioids or alcohol in an attempt to block the effects of naltrexone. 


Naltrexone Interactions With Other Medications

Naltrexone may interact with a few medications such as disulfiram, dextromethorphan, thioridazine, hydrocodone, and oxycodone. Such interactions may change how the treatment works or trigger other serious side effects. So, it’s important to inform your healthcare provider about using other medications and seek medical advice prior to undergoing the treatment. 

Naltrexone is a non-addictive, non-narcotic medication with a low potential for misuse. The efficacy of naltrexone depends on an individual’s commitment to all elements of addiction treatment. 


If you are seeking help with your loved one’s addiction, contact us today or complete our quick contact form below, to speak with an addiction treatment specialist.

If you need help with your substance use disorder, we are here to help you build your confidence and momentum towards the future you want. We provide treatment services for adults with alcohol, opioid, and other substance use disorders. We are currently located in LouisianaMassachusettsNew JerseyNorth CarolinaOhio, Texas, and Washington.

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