Naltrexone can cause liver problems when given in large doses. Stop using this medication and tell your doctor immediately if symptoms of liver problems develop (e.g., persistent nausea, abdominal/stomach pain, yellowing eyes/skin, pale stools, dark urine).

This medication should not be used in patients who already have liver problems (e.g., active hepatitis, liver failure). (See also Side Effects section.)

This medication is used to prevent people who have been addicted to certain drugs (opiates) from taking them again. It is used as part of a complete treatment program for drug abuse (e.g., compliance monitoring, counseling, behavioral contract, lifestyle changes). This medication must not be used in people currently taking opiates, including methadone. Doing so can cause sudden withdrawal symptoms.

Naltrexone belongs to a class of drugs known as opiate antagonists. It works in the brain to prevent opiate effects (e.g., feelings of well-being, pain relief). It also decreases the desire to take opiates.

This medication is also used to treat alcohol abuse. It can help people drink less alcohol or stop drinking altogether. It also decreases the desire to drink alcohol when used with a treatment program that includes counseling, support, and lifestyle changes.

Take this medication by mouth with or without food, usually 50 milligrams once daily or as directed by your doctor. This medication may be given as part of a program where a health care professional will watch you take the medication. In this case, your doctor may order a higher dose (100-150 milligrams) to be taken every 2-3 days to make it easier to schedule clinic visits. Naltrexone may be taken with food or antacids if stomach upset occurs.

A urine test should be done to check for recent opiate drug use. Your doctor may give you another medication (naloxone challenge test) to check for opiate use. Do not use any opiates for at least 7 days before starting naltrexone.

Dosage is based on your medical condition and response to treatment. Your doctor may start you at a lower dose and monitor you for any side effects or withdrawal symptoms before increasing your dose. Take this medication as directed. Do not increase your dose, take it more often, or stop taking it without your doctor's approval.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.

Tell your doctor if you start using drugs or alcohol again.

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.

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.

Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: cough medication (e.g., dextromethorphan), disulfiram, diarrhea medication (e.g., diphenoxylate), narcotic medication (e.g., codeine, hydrocodone, propoxyphene), thioridazine.

This medication may interfere with certain laboratory tests (including drug tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

If overdose is suspected, contact a poison control center or emergency room immediately. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.

Do not share this medication with others.

Laboratory and/or medical tests (e.g., liver function tests) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

Store at room temperature at 77 degrees F (25 degrees C) away from light and moisture. Brief storage between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).

Information last revised March 2013. Copyright(c) 2013 First Databank, Inc.