If you’re considering naltrexone for opioid use disorder or alcohol use disorder treatment, understanding potential side effects is essential for making an informed decision about your care. Naltrexone (including the long-acting injection Vivitrol) is a unique medication for addiction treatment (MAT) that works as an opioid antagonist, blocking the euphoric effects of opioids and alcohol rather than replacing them.
At Porch Light Health, we offer naltrexone therapy at locations throughout Colorado and New Mexico. This comprehensive guide will help you understand what side effects you might experience, how to manage them effectively, and when to seek medical attention.
Naltrexone is a medication approved by the U.S. Food and Drug Administration (FDA) for treating both alcohol use disorder and opioid use disorder. Unlike Suboxone or methadone, which contain opioid agonist properties, naltrexone is a pure opioid antagonist.
How naltrexone works:
According to the Substance Abuse and Mental Health Services Administration (SAMHSA), naltrexone is most effective when combined with counseling and behavioral therapy as part of a comprehensive recovery program.
Key difference from other MAT medications: Naltrexone contains no opioid component, meaning it:
Most people tolerate naltrexone well, and side effects are generally mild and temporary. The side effect profile differs significantly between oral naltrexone and the Vivitrol injection.
Nausea is the most commonly reported side effect of naltrexone, particularly with oral formulations. According to research published in the National Library of Medicine, nausea typically occurs during the first few weeks of treatment and often improves as your body adjusts.
Management strategies:
If nausea persists beyond the first few weeks or becomes severe, contact your healthcare provider. The injectable Vivitrol formulation often causes less nausea than oral naltrexone.
Headaches are common during the initial weeks of naltrexone treatment but typically decrease over time.
Tips for managing headaches:
Persistent or severe headaches should be discussed with your treatment team during your treatment journey.
Some people experience fatigue or decreased energy during the first few weeks of naltrexone treatment. This usually improves as your body adjusts.
Strategies to combat fatigue:
If fatigue persists or interferes significantly with daily activities, discuss dosing adjustments with your provider.
Mild dizziness can occur when starting naltrexone, particularly when standing up quickly.
Safety precautions:
Severe or persistent dizziness warrants medical evaluation to rule out other causes.
The Vivitrol injection commonly causes localized reactions at the injection site (typically the buttocks). According to the FDA, these reactions are usually mild to moderate.
Common injection site reactions include:
Managing injection site reactions:
Most injection site reactions resolve within a few days to two weeks. Severe pain, increasing redness, warmth, or signs of infection require immediate medical attention.
Some people experience difficulty sleeping when starting naltrexone therapy.
Sleep improvement strategies:
If sleep problems persist, your healthcare provider may recommend adjusting dosing time or prescribe short-term sleep aids.
Mild anxiety or nervousness can occur during the initial treatment period, though this is less common than other side effects.
Managing anxiety:
If you have a history of anxiety disorders or if anxiety becomes severe, discuss this with your treatment team. Porch Light Health specializes in dual diagnosis treatment for co-occurring mental health and substance use disorders.
Some people experience decreased appetite during naltrexone treatment, particularly in the first few weeks. This can lead to modest weight loss.
Maintaining healthy nutrition:
Unlike some MAT medications, naltrexone typically doesn’t cause significant weight gain.
Mild muscle aches or joint pain can occur during naltrexone treatment, though this is relatively uncommon.
Relief strategies:
While rare, some side effects require immediate medical attention.
At high doses (much higher than those used for addiction treatment), naltrexone can potentially affect liver function. However, at standard treatment doses (50mg oral or 380mg monthly injection), liver problems are rare.
Risk factors for liver complications:
Warning signs of liver problems:
Before starting naltrexone, your healthcare provider will typically check liver function through blood tests. Regular monitoring may be recommended, especially if you have risk factors. According to the National Institute on Drug Abuse (NIDA), liver problems with naltrexone are uncommon when the medication is used appropriately.
Though rare, severe allergic reactions to naltrexone can occur.
Symptoms requiring immediate medical attention:
Call 911 if you experience symptoms of a severe allergic reaction.
This is the most serious risk associated with naltrexone treatment. Because naltrexone is an opioid antagonist, taking it while opioids are still in your system can cause sudden, severe withdrawal symptoms called precipitated withdrawal.
Critical timing requirements:
Symptoms of precipitated withdrawal include:
To prevent precipitated withdrawal, your healthcare provider may use the COWS assessment (Clinical Opiate Withdrawal Scale) to ensure you’re in sufficient withdrawal before starting naltrexone. Some programs use a naloxone challenge test to confirm opioid clearance.
If you experience precipitated withdrawal:
While naltrexone itself doesn’t directly cause depression, some people report mood changes during treatment. The relationship is complex:
Warning signs to watch for:
If you experience suicidal thoughts:
Porch Light Health provides integrated behavioral health services and psychiatric care to support your mental health during recovery.
Once you start naltrexone, your body loses tolerance to opioids. This creates a serious risk if you stop naltrexone and return to opioid use.
Critical safety information:
If you’re considering stopping naltrexone, discuss it with your treatment team first. Never attempt to “override” naltrexone’s blocking effects by using large amounts of opioids—this can be fatal.
In very rare cases, naltrexone injections have been associated with eosinophilic pneumonia, a serious lung condition.
Symptoms include:
This typically occurs within the first month after injection. Seek immediate medical attention if you experience these symptoms.
Understanding the timeline helps you know what to expect at each stage.
During your first week on naltrexone:
For Vivitrol, injection site reactions peak within the first few days and gradually improve over 1-2 weeks.
By weeks 2-4:
This is when the benefits of naltrexone become more apparent—reduced cravings and less interest in using substances.
After the first month:
The two formulations have different side effect profiles.
Advantages:
Disadvantages:
Common side effects:
Advantages:
Disadvantages:
Common side effects:
Most people find Vivitrol more convenient and easier to tolerate long-term, though individual experiences vary, and patients on low-dose protocols often look into the long-term side effects of low-dose naltrexone as a related consideration. At Porch Light Health, we can help you decide which formulation best fits your needs and lifestyle.
While you can’t prevent all side effects, several strategies can minimize their impact.
For oral naltrexone:
For Vivitrol:
Healthy habits support your recovery and reduce side effects:
Nutrition:
Exercise:
Sleep Hygiene:
Stress Management:
Open dialogue is essential:
At Porch Light Health, we provide ongoing support throughout your treatment journey, including regular check-ins at our clinics throughout Colorado and New Mexico.
Naltrexone has relatively few drug interactions compared to other MAT medications, but some important considerations exist.
Complete contraindication: You cannot take any opioid medications while on naltrexone, including:
Critical safety information:
This antipsychotic medication should not be combined with naltrexone due to increased risk of serious side effects.
When combined with naltrexone, both medications can affect the liver. If used together, careful liver monitoring is required. Some treatment programs successfully use both medications concurrently with appropriate supervision.
Naltrexone can be safely combined with:
Safe to use:
Avoid:
Always read medication labels carefully and consult with your pharmacist if unsure.
Understanding how naltrexone compares to other medications helps inform treatment decisions.
Buprenorphine is a partial opioid agonist, while naltrexone is a pure antagonist.
Naltrexone:
Buprenorphine:
Naltrexone works best for people who:
At Porch Light Health, we offer naltrexone, Suboxone, Sublocade, and Brixadi, allowing us to match you with the best medication for your specific situation.
Methadone is a full opioid agonist requiring specialized clinic attendance.
Naltrexone:
Methadone:
Methadone may be better for people with:
We offer methadone treatment at our Denver and Lakewood clinics for those who need this level of care.
Certain groups require special attention with naltrexone treatment.
Naltrexone’s safety during pregnancy is not fully established. According to the American College of Obstetricians and Gynecologists (ACOG), buprenorphine or methadone are preferred for treating opioid use disorder during pregnancy.
Important considerations:
People with active liver disease or significantly elevated liver enzymes should not take naltrexone.
Liver considerations:
Porch Light Health provides integrated Hepatitis C and HIV treatment alongside addiction services.
Naltrexone can be used in people with mental health conditions, but careful monitoring is needed.
Considerations:
Our psychiatric services ensure comprehensive mental health support during addiction treatment.
Naltrexone blocks all opioid pain medications, making pain management challenging.
Pain management considerations:
Always inform all healthcare providers, especially dentists and surgeons, that you’re on naltrexone.
Naltrexone can be used in adolescents age 18 and older. For younger teens, use is off-label and requires careful consideration.
Seniors may tolerate naltrexone well, but considerations include:
Veterans: We offer specialized support for veterans dealing with opioid or alcohol use disorders.
First Responders: Our first responder program understands unique challenges faced by police, firefighters, and EMS personnel.
Know when to seek help for naltrexone-related concerns.
Call 911 immediately if you experience:
Contact your healthcare provider within 24 hours if you experience:
Discuss at your next appointment:
Common myths can create unnecessary concerns.
Myth: “Naltrexone is just replacing one drug with another.”
Reality: Naltrexone contains no addictive substances. It’s a pure antagonist that blocks opioid receptors without activating them. You cannot get “high” from naltrexone, and it doesn’t cause physical dependence. According to SAMHSA, it’s a non-addictive medication that supports recovery.
Myth: “You can still use opioids while on naltrexone if you use enough.”
Reality: This is extremely dangerous. Attempting to override naltrexone’s blockade by using large amounts of opioids can cause fatal overdose. The blocking effect is strong, and trying to overcome it puts you at severe risk.
Myth: “Naltrexone doesn’t work for alcohol addiction.”
Reality: Naltrexone is FDA-approved for alcohol use disorder and has strong evidence supporting its effectiveness. It reduces heavy drinking days and helps people maintain sobriety. Medication options for alcohol use disorder include naltrexone as a first-line treatment.
Myth: “You can’t take naltrexone if you have Hepatitis C.”
Reality: While naltrexone does require liver monitoring, Hepatitis C itself isn’t an absolute contraindication. Many people with Hepatitis C successfully use naltrexone with appropriate monitoring. Active, acute hepatitis or severe liver disease would preclude use.
Myth: “Vivitrol is better than oral naltrexone.”
Reality: Both formulations are effective. Vivitrol ensures medication adherence since it’s administered monthly by healthcare providers, but oral naltrexone offers more flexibility and lower cost. The “best” option depends on your individual circumstances, preferences, and needs.
Myth: “Naltrexone causes severe depression.”
Reality: Naltrexone doesn’t directly cause depression. However, recovery from addiction can involve confronting difficult emotions that were previously masked by substances. Some people experience mood changes as they adjust to sobriety. This emphasizes the importance of combining medication with therapy and support.
Naltrexone is most effective when combined with comprehensive behavioral health services.
How counseling enhances naltrexone treatment:
At Porch Light Health, we provide:
Our integrated approach treats the whole person, not just the addiction.
Side effects are a consideration with any medication, but naltrexone generally has a favorable side effect profile compared to other addiction treatment medications. Most side effects are mild, temporary, and manageable. The benefits of naltrexone—freedom from active addiction, reduced cravings, normal functioning, and the opportunity to rebuild your life—typically far outweigh any temporary discomfort.
Naltrexone has helped thousands of people achieve long-term recovery from opioid use disorder and alcohol use disorder. With proper medical supervision, honest communication with your treatment team, and commitment to comprehensive recovery, you can successfully manage any side effects while benefiting from this effective medication.
You don’t have to face addiction alone. Recovery is possible, and we’re here to support you every step of the way.
Porch Light Health provides comprehensive naltrexone therapy at locations throughout Colorado and New Mexico. Our experienced team is committed to supporting your recovery with compassionate, evidence-based care.
