SIDE EFFECTS: Nausea, headache, dizziness, anxiety, tiredness, and trouble sleeping may occur. In a small number of people, mild opiate withdrawal symptoms may occur, including abdominal cramps, restlessness, bone/joint pain, muscle aches, and runny nose. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Sudden opiate withdrawal symptoms can occur within minutes after taking naltrexone. Tell your doctor immediately if any of these withdrawal symptoms occur: abdominal cramps, nausea/vomiting, diarrhea, joint/bone/muscle aches, mental/mood changes (e.g., anxiety, confusion, extreme sleepiness, visual hallucinations), runny nose.

Naltrexone has rarely caused serious liver disease. The risk is increased when larger doses are used. This increased risk is balanced by improved likelihood of taking this drug as directed and ease of use when this drug is taken less often (e.g., every other day). Discuss the risks and benefits with your doctor. (See also Warning section.)

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the Revia (naltrexone) Side Effects Center for a complete guide to possible side effects »

PRECAUTIONS: Before taking naltrexone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: taken any type of opioid drugs in the last 7 to 10 days, current opioid dependence (including methadone maintenance), active liver disease/liver failure.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, liver problems.

You should carry or wear medical identification stating that you are taking this drug so that appropriate treatment can be given in a medical emergency.

After stopping naltrexone treatment, you may be more sensitive to lower doses of opioids, increasing your risk of possibly life-threatening side effects from the narcotic (e.g., decreased breathing, loss of consciousness).

This medication blocks the effects of opiate drugs (including heroin) and similar drugs (opioids). However, large doses of heroin or narcotics can overcome this block. Trying to overcome this block is very dangerous and may cause serious injury, loss of consciousness, and death. Make sure you completely understand and accept the risks and benefits of using this medication. Follow your doctor's instructions closely.

Before having surgery or any medical treatment, tell your doctor or dentist that you are taking this medication.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.