Naltrexone is not always blocked by past opioid use. However, it can be dangerous. If your body still holds opioids, naltrexone can trigger sudden withdrawal.
Give your prescriber your full opioid history. Also list every medicine you take before starting. Do not guess when it is safe to begin.
This guide covers opioid safety for those on naltrexone for alcohol use disorder. Read our guide to medications for alcohol use disorder for extra details. We are an editorial team that researches health topics. We are not a treatment provider, nor do we provide medical review.
Naltrexone and Opioid Use: Key Points
Naltrexone is approved to treat alcohol use disorder.[1] Its extended-release injectable form is also approved for opioid use disorder, but approval and use rely on the specific formulation.[2] It blocks opioid receptors.[2] You may still take naltrexone for alcohol use disorder if you used opioids before. However, using opioids now or recently shifts the safety outlook. Our guide to naltrexone for alcohol use disorder explains how the medication works and what to expect.
Overdose deaths are a serious issue in the U.S. In 2023, there were 105,007 drug overdose deaths.[3] These numbers show why safety matters. They cannot show how well naltrexone works or its risks.
105,007
U.S. drug overdose deaths in 2023[3]
It is vital to grasp how naltrexone and opioids interact. Find more options in our guide to medications for alcohol use disorder.
How Naltrexone and Opioids Act on Each Other
Opioid receptors in the body are blocked by naltrexone.[2] This lowers or stops what opioid drugs do.[4]
Naltrexone can affect how opioid pain medicines work. If you take it, opioids may not act as planned.[4] Be sure to discuss your pain care with your doctor.
| Situation | What May Happen | Why It Matters | Safer Next Step |
|---|---|---|---|
| Naltrexone blocks opioid receptors | Naltrexone may block opioid medicines used for pain.[5] | Pain treatment may be affected.[5] | Tell your prescriber you take naltrexone if you need pain care. |
| You take naltrexone after recent opioid use | If you are physically dependent on opioids or start naltrexone too soon after opioid use, severe withdrawal can occur.[5] | The risk depends on physical dependence and timing.[5] | For severe withdrawal symptoms, call 911 or go to the nearest emergency room now. If no emergency symptoms are occurring, contact your prescriber promptly. |
Naltrexone Opioid Withdrawal: The Importance of Timing
Precipitated withdrawal is an urgent safety issue. It is different from spontaneous withdrawal that occurs when a person who is physically dependent stops opioids.[5] Naltrexone can trigger severe withdrawal if a person is physically dependent on opioids or starts naltrexone too soon after opioid use.[5] For a closer look at what to expect, our guide to opioid withdrawal covers the symptoms and timeline in detail. For a deeper dive into the process, our guide to opioid detox duration explains how long the phase typically takes.
This kind of withdrawal can be very bad.[5] Some people need hospital care, and some may need intensive care.[5] Do not manage this at home. Do not pick a safe start date by yourself.
If you have severe withdrawal symptoms, call 911 or go to the nearest emergency room now. Talk to your prescriber before starting naltrexone if you used opioids lately or are unsure when you last did.[5] They can check for recent opioid use and any physical dependence before care begins.[5]
Will a Prior Opioid History Affect Starting Naltrexone?
Just because you used opioids before does not mean you need them today. That history alone does not make naltrexone safe to start. The FDA label notes that naltrexone triggers withdrawal symptoms in people with physical opioid dependence.[5] Before you start, doctors must screen for recent use and opioid dependence.[5]
Your clinician asks lots of questions. They need to know which opioids you took and when. This includes prescriptions, over-the-counter items, and other sources. If the doctor misses your opioid use, withdrawal can occur.[5] No one day count fits all people. Safe timing depends on your case and the exact opioid. Starting too early can cause withdrawal that is bad enough to need hospital care.[5]
Prepare for your visit by using this checklist. You can also read our guide on asking your doctor about medication for more tips.
What to Tell the Prescriber
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How Naltrexone Affects Opioid Pain Meds
Opioid pain medicines lose their effect when naltrexone blocks them.[5] This makes using opioids for pain hard. Be sure to discuss this with your doctors.
- Tell your naltrexone prescriber. Share details about any upcoming surgery, dental work, or new pain issues.
- Notify all involved clinicians. Let surgeons, dentists, anesthesiology teams, and emergency staff know you take naltrexone. Tell them well in advance.
- Ask for a coordinated plan. Request that your care team work together to manage your pain safely.
- Disclose immediately in emergencies. If you have urgent pain, tell the staff you take naltrexone right away. Do not wait to call your usual prescriber first.
Do not change or stop your naltrexone dose by yourself. Check with your prescriber before you adjust your medication plan.
Doctors may use nonopioid options or regional pain methods to manage discomfort. Your care team picks the best option for you. The facility must be set up for cardiopulmonary resuscitation.[5] Keep a written note on your naltrexone use so providers can treat you well.[5]
Overdose Risk and When to Get Emergency Help
Naltrexone blocks the effects of opioids, but it does not protect you from an overdose if you use them anyway. If you stop using opioids for a while, your body’s tolerance can fall.[5] Taking the same dose you had before may be too high for your body to handle safely.
Trying to overcome the block or using opioids as the medication wears off can lead to a fatal overdose. This is a critical part of naltrexone safety and opioid use awareness.
Act fast if you think someone is overdosing. Look for signs like not waking up, or breathing that is slow, shallow, or has stopped.
- Call 911 right away. Do not wait to see if the person wakes up.
- Use naloxone if you have it. Follow the instructions on the package. Naloxone can reverse an opioid overdose, but its effects may wear off before the opioid does.[6]
- Stay with the person. Monitor their breathing until emergency responders arrive.
Always seek professional help after any suspected overdose.
If you or a loved one has a slip, it is not a moral failure. It means the current plan needs to change. Read our guide on managing setbacks with support to learn what to do after a relapse.
Comparing Safety of Oral and Extended-Release Naltrexone
Two main forms of naltrexone exist: an oral tablet and an extended-release injectable product.[7] The way each is given differs. Each form also brings its own safety questions for your care team.
The table below shows key differences. It is not a guide for taking opioid pain medicine safely. It does not say when you can start naltrexone. Only a prescriber can pick the right timing for your history.
| Feature | Oral Naltrexone | Extended-Release Injectable Naltrexone |
|---|---|---|
| Formulation | Tablet taken by mouth | Microsphere suspension for injection |
| Administration | Taken by the patient at home | Administered by a healthcare professional |
| Specific Risks | General medication side effects | Injection site reactions, which are distinct from tablet risks |
| Starting After Opioid Use | Ask your prescriber how long you must be opioid-free to avoid precipitating withdrawal[5] | Ask your prescriber how long you must be opioid-free to avoid precipitating withdrawal[5] |
| Duration of Opioid Blocking | Ask how long the blocking effect lasts and how it may affect pain care[5] | Ask how long the blocking effect lasts and how it may affect pain care[5] |
| Planning for Procedures or Urgent Pain | Discuss with your prescriber how to manage pain if you need opioid relief during a procedure or emergency[5] | Discuss with your prescriber how to manage pain if you need opioid relief during a procedure or emergency[5] |
A healthcare professional gives the extended-release injectable product.[5] This product carries risks at the injection site. These include reactions where the shot is given.
The medication works by blocking opioid receptors.[2] Its effects can last after a dose, and the time varies by formulation and your situation.[5] Do not use this table to decide if opioid pain medicine is safe.
Our related guide has more on managing medication side effects if you wonder how the medication affects your body.
Talk to Your Prescriber: A Safer Path Forward
Quizzes cannot show if opioids are gone from your body. They cannot say if it is safe to start naltrexone. A doctor makes that decision. Use this check to prepare for your chat with your prescriber.
What Should I Discuss Before Starting Naltrexone?
This self-check is for information only and isn't a diagnosis. It cannot determine safe timing for medication.
Emergency Warning: If you have seizures, severe confusion, hallucinations, a high fever or racing heart during withdrawal, signs of an overdose, or thoughts of suicide or self-harm, get emergency help now—call 911 or go to an emergency room. For suicidal thoughts, call or text 988; call 911 or go to an emergency room for immediate danger or if you cannot stay safe.
Action Steps Before Starting
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Frequently Asked Questions
What happens if you take naltrexone with opioids?
If you still have opioids in your body, naltrexone can cause sudden withdrawal. You may feel sick to your stomach, vomit, or have diarrhea. You might also have muscle aches and anxiety.[8] Do not try to guess if this is safe. Call your prescriber right away. If you have severe symptoms, call 911 or go to the nearest emergency room now.
What drugs should not be taken with naltrexone?
Tell your prescriber and pharmacist about all your medicines. Include prescription drugs, over-the-counter items, and other substances. Some products that do not look like painkillers may still contain opioids, such as certain cough syrups, anti-diarrheal medicines, or combination pain relievers. A clinician or pharmacist should check your complete medication list to identify these interactions, rather than relying on this article as an exhaustive list.
Does naltrexone block opioid receptors?
Yes, naltrexone blocks opioid effects at receptors.[2] It does not activate them. The drug does not remove opioids from your body. It also does not make using opioids safe. Never try to beat the block by taking more opioids.
How does naltrexone help with opioid addiction?
Naltrexone is one of the medications approved to treat opioid use disorder.[2] In the context of naltrexone and opioid use disorder, the medication works by blocking opioid receptors so that opioid drugs can no longer cause feelings of pleasure.[2] This differs from its role in alcohol use disorder, where it is also approved to help reduce cravings and heavy drinking.[2] Naltrexone is one treatment option among others, and it is often used alongside counseling or therapy. A prescriber must assess your specific health history and goals to determine if it is appropriate for you. They can help you compare this option with other treatments without providing specific dosing instructions here.
Why don't doctors like naltrexone?
Doctors do not have a general dislike for naltrexone. Clinicians look at your goals and health history first. They may delay starting naltrexone or choose another treatment if there is a risk of precipitated withdrawal because opioids are still in your body, if you need ongoing opioid pain treatment, or if other factors fit your specific treatment goals better. If a provider suggests a different option, ask why they chose it for you. This helps you understand the plan for your care.
Can I take pain meds while on naltrexone?
Do not assume opioid pain meds will work normally on naltrexone. The blocking effect can last for different amounts of time.[5] It depends on the form of the drug and your body. Do not stop or change naltrexone on your own. Talk to your prescriber first. Tell any doctor treating your pain that you take naltrexone so they can pick safer options.
