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Weight Loss

14 min read

Naltrexone weight loss — the pros and cons

Written by Douglas Helm

Published: Mar 21, 2024

Medically Reviewed by Dr. Sheelu Bhatnagar

Table of contents

Naltrexone is a medication that’s U.S. Food and Drug Administration (FDA)-approved to treat alcohol and opioid use disorders, but may also result in weight loss. In this article, we discuss what naltrexone is and how it works and the potential benefits of naltrexone weight loss. We also discuss costs, side effects, and alternative weight loss medications, like Contrave which combines naltrexone with the antidepressant bupropion.

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What is naltrexone?

Naltrexone is a medication in the drug class called opioid antagonists. While by itself it’s an FDA-approved drug to treat alcohol use disorder and opioid dependence, it may also lead to weight loss. Because naltrexone itself isn’t approved for weight loss, using it for weight loss is an off-label use. 

Naltrexone, also known as naltrexone hydrochloride, is a generic medication available as 25-, 50-, and 100-milligram oral tablets. A brand-name version, called Vivitrol, is available as a single-dose vial of an injectable suspension that contains 380 mg of naltrexone. Vivitrol is taken once a month and has to be injected by a healthcare professional.

A fixed-dose combination of naltrexone and bupropion (naltrexone-sustained release [SR] 32 milligrams and bupropion SR 360 milligrams) is sold under the brand name Contrave and is FDA-approved to treat obesity. More on that below.

How does naltrexone weight loss work?

Naltrexone affects the brain’s reward system by blocking the euphoric and sedative effects that alcohol and opioids, such as heroin, morphine, and codeine, cause. By blocking the feel-good effects of drugs and alcohol, naltrexone prevents people from becoming intoxicated and dependent on them, so they no longer crave them.

Naltrexone may also reduce food cravings and food consumption by blocking the action of a specific endorphin (the beta-endorphin) at an opioid receptor in the brain (a part of the brain receptive to the effects of opioids). Put simply, naltrexone blocks the pleasure people get from eating, so they eat less.

A study of naltrexone and reward-based eating on food cravings among obese women found that the opioid-blocking effects of high-dose (50 milligram) naltrexone reduced the reward eating drive (RED) and the intensity of food cravings for sugary and fatty foods. 

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The pros of using naltrexone for weight loss

Because naltrexone alone isn’t approved for weight loss, there are few studies on its effect on weight. Those that have been done are small. And more research is needed, but the few available studies show that naltrexone may offer some benefits for weight loss.

Naltrexone may curb appetite and reduce food intake. A small study on food intake and appetite changes during eating done with males taking naltrexone found that naltrexone was effective at reducing appetite. Naltrexone made pleasant tastes unpleasant and participants ate significantly less food when taking 50 milligrams of naltrexone a day.

A comparison study of bupropion HCI-naltrexone HCI vs naltrexone vs placebo found that naltrexone may also lead to minor weight loss. It concluded that the portion of 419 patients with uncomplicated obesity taking 48 milligrams of immediate-release naltrexone lost an average of 1.7% loss of body weight after 24 weeks.

Alternatives to naltrexone for weight loss

There are alternative prescription weight loss pills to naltrexone. The most popular include the weight loss injections Zepbound (tirzepatide),  Wegovy (semaglutide), and Saxenda (liraglutide). Alternative weight loss pills include Qysmia (phentermine-topiramate), Adipex-P (phentermine), and Contrave (bupropion HCI-naltrexone HCI). These medications are all FDA-approved for weight loss or weight management as part of a weight loss program that includes exercise and dietary changes. 

There are also FDA-approved over-the-counter weight loss pills like Alli (orlistat). Each medication comes with its own pros and cons, so make sure to discuss options with your healthcare provider.

Contrave is a good alternative if you’re interested in naltrexone’s ability to help control food cravings. 

Naltrexone for weight loss in Contrave (bupropion HCI-naltrexone HCI) 

Contrave is a weight loss pill that combines naltrexone and bupropion. Bupropion is a norepinephrine and dopamine reuptake inhibitor antidepressant. It’s FDA-approved to treat adult depression, seasonal affective disorder, and to help people stop smoking. 

Contrave was approved for weight loss by the FDA in 2014. It’s used to help adults lose weight and keep the weight off provided they have a body mass index (BMI) equal to or more than 30 or a BMI equal to or more than 27 with at least one weight-related health condition, such as type 2 diabetes, high blood pressure, and/or high cholesterol. It should be used as part of a medically supervised weight loss plan that includes a reduced-calorie diet and increased physical activity. 

One oral Contrave extended-release tablet contains 8 milligrams of naltrexone and 90 milligrams of bupropion. Patients start with a smaller dose and work up to a maintenance dose as follows.

WeekMorning doseEvening dose
11 tablet0 tablets
21 tablet1 tablet
32 tablets1 tablet
4 and on (maintenance dose)2 tablets2 tablets

How Contrave works for weight loss

An analysis of four studies concluded that a significantly higher number of participants lost 5 to 10% body weight on naltrexone-bupropion compared to participants on placebo. 

The previously mentioned comparison study of bupropion-naltrexone vs naltrexone vs placebo of 419 patients with uncomplicated obesity taking 48 milligrams of immediate-release naltrexone alone lost an average of 1.7% loss of body weight after 24 weeks. Participants taking a combination therapy of 400 milligrams of bupropion and 16 milligrams of naltrexone lost roughly 6.5% body weight in the same 24 weeks.

Side effects of Contrave (bupropion HCI-naltrexone HCI)

Almost all medications have side effects. If you choose to try Contrave and your provider agrees, its common side effects include:

  • Nausea
  • Constipation
  • Vomiting
  • Headaches
  • Dizziness
  • Dry mouth
  • Trouble sleeping
  • Diarrhea

Contrave can also increase your risk of seizures and suicidal thoughts. Other serious side effects include liver damage, manic episodes, visual problems, increased risk of low blood sugar, and increases in blood pressure or heart rate. Some individuals may have a severe allergic reaction to bupropion. Seek emergency medical attention if you experience trouble breathing, chest pain, swelling, skin rashes, itching, hives, fever, painful sores, or other symptoms of an allergic reaction.

Higher doses may increase your likelihood of side effects and complications. Contrave can cause withdrawal symptoms, so make sure to follow your health provider’s instructions. Find a complete list of side effects in Contrave’s medication guide.

Cost of Contrave (bupropion HCI-naltrexone HCI) and naltrexone

The cost of Contrave is $667.84 for a 1-month supply of 120 tablets according to Prices can vary depending on your insurance coverage and coupons. 

Contrave’s manufacturer, Currax Pharmaceuticals, offers 2 ways to save on Contrave.

  • Through its coupon savings card program you can pay as little as $20 for a 1-month supply if you have insurance. If you don’t have insurance or your insurance doesn’t cover Contrave, you pay no more than $199 for a 1-month supply if you qualify.
  • You can also sign up for the CurAccess Program. This program makes the price of Contrave $99 per month with free shipping included. You may pay even less with insurance coverage. 

The cost of naltrexone varies depending on the form, brand, and insurance coverage. A 30-day supply of 50-milligram generic naltrexone oral tablets costs $47.93. The injectable Vivitrol costs $1,737.59 for a monthly injection. (Costs are per Vivitrol does offer a savings program, where you could pay as little as $0 a month.

Insurance coverage may reduce your out-of-pocket cost for Contrave or naltrexone. If you have insurance, check with your provider to determine your coverage. 

Your state or insurance provider may require prior authorization for naltrexone. And your insurance provider may require prior authorization for Contrave. Prior authorization is when your health plan won’t cover a medication unless they approve doing so first.

If your provider prescribes naltrexone off-label for weight loss, it may not be covered by insurance. Ask your insurance provider for details.

Key takeaway 

Weight loss can be a side effect of naltrexone, but it’s approved to treat substance abuse disorders, not obesity or overweight. If you’re looking for a medical weight loss solution, consider talking to your doctor about Contrave. Studies show that Contrave results in more weight loss than naltrexone alone. A healthcare provider can help you find the best weight loss treatment based on your health needs and goals.

Get help with weight loss when you find a provider on Klarity 

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The information provided in this article is for educational purposes only and should not be construed as medical advice. Always seek the guidance of a qualified healthcare professional with any questions or concerns you have regarding your health.

How we reviewed this article: This article goes through rigorous fact-checking by a team of medical reviewers. Reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the author.

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