Naltrexone: What It's Used For, How to Take, Doses & Side Effects

Naltrexone is prescribed for the treatment of alcoholism and other substance abuse disorders. It works by inhibiting areas in the brain that are responsible for pleasure sensations when consuming alcohol, opioid drugs or and other illicit substances, thereby reducing the desire to abuse these substances. 

This medication can be obtained in pharmacies in the form of a tablet containing 50 mg of naltrexone hydrochloride. It is sold only with a prescription.

Naltrexone can also be found as an injectable, to be applied by a doctor or nurse for use in hospital settings. This form is more commonly used for emergency treatment of opioid poisoning.

What it's used for

Naltrexone is indicated for the treatment of:

• Alcoholism
• Opioid dependence, such as morphine or heroin
• Poisoning by opioid substances

Naltrexone works by binding to mu-type opioid receptors in the brain, which blocks the effects of alcohol and opioids. This reduces the desire to drink or consume opioids, and can also prevent opioid intoxication.

This medication should only be used if prescribed, and is not indicated for other conditions, such as shortness of breath, tiredness or depression.

In some cases, the doctor may prescribe naltrexone to be used with other opioids, like morphine or oxycodone, for the treatment of chronic pain. It can be used in cases of cancer treatment, for example, to prevent side effects like constipation or opioid overdose.

Does naltrexone help you lose weight?

Naltrexone has been used in low doses to help lose weight when combined with bupropion, as these substances together help control appetite and intense desire for food. By controlling these aspects, total food intake can be reduced, leading to weight loss.

However, naltrexone alone is not recommended for weight loss.

How to take and doses

The way naltrexone is used depends on the form prescribed. Recommended dosing is as follows: 

1. Naltrexone tablet 50 mg

Naltrexone in tablet form should be taken orally, with a glass of water, before or after a meal.

The normally recommended doses of naltrexone tablets for adults are:

• Treatment for alcoholism: the normally recommended dose is one 50 mg tablet per day, always taken at the same time, for up to 12 weeks of treatment, or as per medical advice;
• Treatment for opioid dependence: this medication should only be started after the body has detoxed from the opioids for at least 7 to 10 days. The normally recommended initial dose is 25 mg per day, which can be increased by the doctor to 50 mg per day if the person does not experience symptoms of opioid withdrawal.

Naltrexone doses can be modified by the doctor depending on response to treatment. An alternative schedule of doses may be indicated for the treatment of opioid dependence.

To treat opioid dependence, the doctor may recommend 50 mg of naltrexone per day every day of the week, plus an additional dose of 100 mg on Saturday. Another option that may be indicated is 100 mg of naltrexone every other day or 150 mg every 3 days.

It is important to maintain dosing as prescribed at the times established by your doctor. You should not stop treatment on your own.

2. Injectable naltrexone

Injectable naltrexone is used in hospital settings and must be applied directly to the vein, muscle or skin by a doctor, nurse or trained healthcare professional. Dosing should be determined by a doctor, depending on the severity of the symptoms caused by opioid poisoning.

Possible side effects

The most common side effects that may occur during treatment with naltrexone include nausea, headache, dizziness, nervousness, fatigue, insomnia, vomiting, anxiety, drowsiness, abdominal pain, cramps, joint or muscle pain, nausea or vomiting.

In addition, naltrexone can cause depression, suicidal ideation, attempted suicide, diarrhea, constipation, increased thirst, nasal congestion, increased blood pressure, palpitations or tachycardia.

During treatment with naltrexone, you should avoid consuming alcohol, as naltrexone and alcohol together can cause liver damage, which can present iwth symptoms such as fever, chills, loss of appetite, abdominal pain, yellowing of the skin and eyes, pale stools or dark urine. If you notice these symptoms, you should proceed to the hospital immediately.

Contraindications for use

Naltrexone should not be used by children or adolescents under 18 years of age nor by pregnant or breastfeeding women. It is not advised for people with a history of liver failure, acute hepatitis, or allergies to naltrexone hydrochloride or any of the components in the medication's formula.

This medicine should also not be used by people who have used opioids in the 7 to 10 days before starting treatment.

Furthermore, naltrexone should not be used by people who are being treated for pain, cough or diarrhea with opioid analgesics, such as morphine or codeine, for example, as it may reduce the effectiveness of the treatment.

Drug interactions

Naltrexone can interact with other medications, particularly those that affect liver functioning. Medications like acetaminophen, corticosteroids, antifungals, cyclosporine in high doses, medicinal plants and nutritional supplements (like comfrey, kava kava or black cohosh) should be avoided during treatment when possible.

It is important to inform your doctor and pharmacist of any  medications, herbs, or supplements that you are taking to prevent drug interactions that may interfere with other treatments or increase the risk of side effects.

Be sure to avoid taking any new medications if you are on naltrexone treatment.