Naltrexone is a prescription drug that’s used to treat alcohol use disorder and opioid use disorder. The drug comes as an oral tablet. It’s usually taken once per day.
Naltrexone is prescribed for adults to treat:
Naltrexone belongs to a group of drugs called opioid antagonists. This article describes the dosage of naltrexone, as well as its strength and how to take it. To learn more about naltrexone, see this in-depth article.
This section describes the usual dosages of naltrexone. Keep reading to learn more.
What is naltrexone’s form?
Naltrexone is available as:
- an oral tablet
- a liquid solution that’s given as an injection into a muscle
This article will focus on the oral form of naltrexone. The injectable form of naltrexone is also available as the brand-name drug Vivitrol.
What strength does naltrexone come in?
Naltrexone oral tablet comes in a strength of 50 milligrams (mg).
What are the usual dosages of naltrexone tablet?
The information below describes dosages that are commonly used or recommended. But be sure to take the dosage your doctor prescribes for you. They’ll determine the best dosage to fit your needs.
Dosage for alcohol use disorder
The typical naltrexone dosage for adults with alcohol use disorder is 50 mg once per day.
Dosage for opioid use disorder
For adults with opioid use disorder, the typical dosage of naltrexone is 25 mg for the first dose, then 50 mg once per day.
Is naltrexone used long term?
Yes, naltrexone is usually used as a long-term treatment. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely take it long term.
The dosage of naltrexone you’re prescribed may depend on several factors. These include:
If you’re prescribed Naltrexone tablet, you’ll typically swallow it whole. If you have trouble swallowing tablets, see this article for tips on how to take this form of medication.
The tablet is scored (has a break line) so you can split it in half if needed. But you should check with your doctor before crushing or chewing these tablets.
You can take naltrexone with or without food.
Accessible drug containers and labels
Some pharmacies provide medication labels that:
- have large print
- use braille
- feature a code you can scan with a smartphone to change the text to audio
Your doctor or pharmacist may be able to recommend pharmacies that offer these accessibility features if your current pharmacy doesn’t.
Let your pharmacist know if you have trouble opening medication bottles. They may have tips to help, or they may be able to supply naltrexone in an easy-open container.
If you miss a dose of naltrexone, take it as soon as you remember. But if it’s almost time for your next dose, skip the missed dose and take your next dose at its usual time. If you’re not sure whether you should take a missed dose, talk with your doctor or pharmacist.
If you need help remembering to take your dose of naltrexone on time, try using a medication reminder. This can include setting an alarm or using a reminder app on your phone.
Do not take more naltrexone than your doctor prescribes, as this can lead to harmful effects.
What to do in case you take too much naltrexone
Call your doctor right away if you think you’ve taken too much naltrexone. You can also call 800-222-1222 to reach America’s Poison Centers or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.
Taking naltrexone does not lead to dependence. With dependence, your body needs the drug to feel like it usually does. If you stop taking a drug you’re dependent on, you may have withdrawal symptoms. You won’t have withdrawal symptoms if you suddenly stop taking naltrexone.
If you have questions about naltrexone and the risk of dependence or withdrawal symptoms, talk with your doctor.
Below are answers to some commonly asked questions about naltrexone’s dosage.
Can naltrexone be used for weight loss? If so, what’s the dosage?
No, naltrexone is not used for weight loss.
Because naltrexone isn’t used for weight loss, the drug manufacturer doesn’t provide recommended dosages for this use.
However, Contrave (naltrexone/bupropion) is a combination drug that’s approved for weight loss. It contains naltrexone with another active ingredient* called bupropion. To learn more about this and other treatment options for weight loss, talk with your doctor.
* An active ingredient is what makes a drug work.
How long does it take for naltrexone to start working?
Naltrexone starts to work after your first dose. Because of how the drug works, you likely won’t feel the drug working in your body. But your doctor will monitor you during treatment to check whether the drug is working to treat your condition.
If you have other questions about what to expect from your naltrexone treatment, talk with your doctor.
The sections above describe the usual dosages provided by the manufacturer. If your doctor recommends naltrexone for you, they’ll prescribe the dosage that’s right for you.
Remember, you should not change your dosage of naltrexone without your doctor’s recommendation. Only take naltrexone exactly as prescribed. Talk with your doctor if you have questions or concerns about your current dosage.
Here are some examples of questions you may want to ask your doctor:
- How long does a dose of naltrexone last?
- Should my dosage change if naltrexone isn’t working well enough for me?
- Does my dosage of naltrexone need to change if I’m taking other drugs along with it?
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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.