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. You may need to stop certain opiate drugs (such as methadone) 10 to 14 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 right away 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. Discuss the risks and benefits with your doctor. Stop using this medication and tell your doctor right away if you develop symptoms of liver disease, including: persistent nausea/vomiting, severe stomach/abdominal pain, dark urine, yellowing eyes/skin.
A very serious allergic reaction to this drug is rare. However, get medical help right away 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.