Key Points

Dizziness, drowsiness, sedation and fainting have all been reported as possible side effects with naltrexone treatment. Avoid driving, operating heavy machinery, or performing other hazardous activities until you know how naltrexone may affect you.

Naltrexone is approved for the treatment of alcohol use disorder or opioid use disorder (OUD) in adults, along with counseling, as a medication-assisted treatment (MAT) option. Naltrexone is not a cure for drug addiction or alcoholism.

• In patients receiving extended-release naltrexone injection (brand name: Vivitrol) for treatment of alcohol use disorder (alcoholism), sedation was reported to occur in 5% of patients receiving Vivitrol compared to 1% of those in the placebo (inactive treatment) group.
• Dizziness or fainting occurred in 13% of those using Vivitrol injection compared to 4% in the placebo group.
• In studies of patients being treated for alcoholism with naltrexone tablets, extreme drowsiness (somnolence) was reported to occur in 2% of patients and dizziness occurred in 4% of patients.

Why else might I be sleepy with naltrexone?

Depression

If you find that you feel tired or sleepy all the time while taking naltrexone, contact your doctor. This may be a sign that you are experiencing a depressed mood. Depression can lead to suicidal thoughts, suicidal behavior or suicide.

Tell your doctor if you have a history of depression, attempted suicide, or other mental health disorders before you start naltrexone treatment. Inform your family you are taking naltrexone and to be aware of any mood changes you may experience. They should call a doctor right away if you become depressed or experience symptoms of depression.

Liver toxicity

If you are feeling tired, have pain in your stomach area lasting more than a few days, dark-colored urine, or yellowing of the whites of your eyes, you may have a serious liver problem. Contact your doctor immediately. Your treatment will need to be evaluated.

Opioid Use or Overdose

If you become very drowsy with slowed breathing, this may be a sign that you are having an opioid overdose, which may lead to death, if you have taken opioids with naltrexone.

You or someone close to you should get emergency medical help right away if you have:

• trouble breathing
• become very drowsy with slowed breathing
• have slow, shallow breathing (little chest movement with breathing)
• feel faint, very dizzy, confused, or have unusual symptoms

When taking naltrexone tablets or Vivitrol injection, it is important that you tell your family and the people closest to you that you may can have increased sensitivity to opioids, even at lower doses. You are at risk of an overdose if you take opioids during treatment with naltrexone.

Drug interactions

Combining naltrexone with other medicines that may cause drowsiness or sedation may worsen this side effect.

Use caution when combining these types of medications and ask your pharmacist or doctor to check for important drug interactions each time you get your medicine or prescription. Be sure to tell them about any herbal products, vitamins or other OTC products you use.

Other common side effects with naltrexone

Naltrexone (Vivitrol) may precipitate a mild to possibly severe withdrawal in individuals physically dependent on opiates.

In addition to sleepiness, other common side effects reported with naltrexone include:

• stomach cramping or pain
• decreased appetite
• headache
• symptoms of a cold
• dizziness
• anxiety, nervousness
• trouble sleeping
• joint and muscle pain
• nausea or vomiting (usually decreases over time)
• fatigue
• toothache
• injection site reaction like pain or tenderness

What does naltrexone treat?

Naltrexone is approved by the FDA for the treatment of alcohol use disorder and opioid use disorder when added to a medically supervised behavior modification program.

• Naltrexone is used to prevent relapse in people who became dependent on opioid medicine and then stopped using it. Naltrexone can help keep you from feeling a "need" to use the opioid. You should not start naltrexone therapy until you have been opioid-free (including tramadol) for at least 7 to 14 days after your last opioid use.
• Naltrexone can help lower your urge to drink alcohol, which may help you slow down or stop your drinking. Naltrexone will not lower the effects of alcohol you have recently consumed. You should stop drinking before starting naltrexone.

Related: Opioid Use Disorder: These Treatments Are Available, Now

In OUD, oral naltrexone tablets have not been shown to be more effective than placebo (an inactive pill) as patients do not consistently stay on treatment as prescribed.

Naltrexone works by blocking the opioid receptor and effects of opioids, such as heroin or opioid pain medicines. It also appears to have an effect on opioid pathways in alcohol use disorder. Naltrexone is considered a full opioid antagonist that blocks the euphoric actions of narcotics (meaning it can't lead to addiction or a "high").

If you take opioids or opioid-containing medicines, you must stop taking them before
you start receiving naltrexone. Your doctor will direct you on the best and safest way to do this. Any doctor may prescribe naltrexone.

Naltrexone is available as a long-acting intramuscular injection (brand name: Vivitrol) or as generic 50 mg oral tablets. There is no generic available for Vivitrol to date.

This is not all the information you need to know about naltrexone (Vivitrol) for safe and effective use. Review the full naltrexone and Vivitrol information here. Discuss this information and any questions you have with your doctor or other health care provider.