At a glance

What it is

Two products, one ingredient in common

Naltrexone is an opioid receptor blocker. At the usual 50 mg tablet dose, it is approved to treat alcohol dependence and to block the effects of opioids.

Contrave is a fixed-dose extended-release tablet that combines naltrexone with bupropion. The idea is that the two act on appetite and reward pathways in the brain together. The label describes it as a combination of an opioid antagonist and an aminoketone antidepressant. It is approved, with a reduced-calorie diet and more physical activity, to reduce excess body weight and keep it down long term in adults with obesity, or with overweight plus at least one weight-related condition. The label notes its effect on heart attacks and strokes has not been established.

Low-dose naltrexone, usually 1.5 to 4.5 mg a night, is a separate idea. It is not Contrave and it is not studied the same way. It is used off-label for several conditions, and weight is one the evidence barely covers.

The bupropion half is covered on its own page: bupropion.

Who it is for

Who it is for, and who it is not for

A physician may consider Contrave for an adult who needs a weight medicine but cannot or should not take a GLP-1. Examples are a past reaction to one, a family history that rules one out, a plan to conceive, or a decision to come off one. The guideline summaries I reviewed place naltrexone-bupropion as an alternative when GLP-1 agents are unavailable or unsuitable, with weaker evidence behind it.

It is also not recommended in severe liver impairment or end-stage kidney disease, and it should be stopped if pregnancy is recognized. People with a history of major depression or other psychiatric illness need a careful discussion first, because of the boxed warning below.

Low-dose naltrexone has no approved weight indication, so no label defines who it is for. The same opioid caution applies: if you take any opioid, tell the physician before anything else.

How it is taken

How Contrave is taken

Each tablet holds 8 mg of naltrexone and 90 mg of bupropion. The label raises the dose over four weeks: one tablet in the morning in week 1, one morning and one evening in week 2, two in the morning and one in the evening in week 3, then two morning and two evening from week 4. That reaches 32 mg of naltrexone and 360 mg of bupropion a day, which is the top recommended dose. Tablets must be swallowed whole, and the label advises against taking them with a high-fat meal.

The label caps the dose at one tablet morning and evening in moderate or severe kidney impairment, moderate liver impairment, and with CYP2B6 inhibitors such as clopidogrel.

The evidence

What the trials show

Contrave

COR-I randomized 1,742 adults at 34 US sites to naltrexone 32 mg plus bupropion, naltrexone 16 mg plus bupropion, or placebo for 56 weeks, with diet and exercise advice. Mean weight change was a loss of 6.1 percent on the full dose and 1.3 percent on placebo. About 48 percent of the full-dose group lost at least 5 percent of body weight, versus 16 percent on placebo. Only half the participants finished 56 weeks, and the main analysis carried forward the last recorded weight for people who left.

COR-BMOD enrolled 793 adults for 56 weeks and added an intensive group behavior program. Mean loss was 9.3 percent with Contrave versus 5.1 percent with placebo, in participants who took the drug and had a follow-up weight. COR-Diabetes randomized 505 adults with type 2 diabetes: weight fell 5.0 percent versus 1.8 percent, and A1c fell 0.6 versus 0.1 points.

Trials in different populations are not directly comparable. As context, a semaglutide 2.4 mg trial in 1,961 adults without diabetes reported a mean 17.3 percent loss at 68 weeks. Contrave’s average effect is smaller. Individual results vary a great deal, and some people respond well.

Low-dose naltrexone

I did not find a randomized trial built to test low-dose naltrexone for weight loss, and the obesity guidelines I reviewed do not mention it. Reports of benefit tend to come from people with pain or inflammatory conditions, where weight may follow other changes. That is not evidence that it lowers weight directly.

Safety

Warnings and side effects

In the label’s pooled trials, nausea affected 32.5 percent of people on Contrave versus 6.7 percent on placebo. Constipation was 19.2 versus 7.2 percent, headache 17.6 versus 10.4, vomiting 10.7 versus 2.9, dizziness 9.9 versus 3.4, insomnia 9.2 versus 5.9, and dry mouth 8.1 versus 2.3 percent.

• Blood pressure and heart rate. Both can rise. They should be checked before and during treatment.
• Seizures. Risk is dose related. Taking more than directed raises it.
• Opioids. Naltrexone blocks opioid pain medicines. After stopping Contrave, you may be more sensitive to opioids than before.
• Liver. Cases of hepatitis and liver dysfunction have been seen with naltrexone.
• Eyes. Bupropion can trigger angle-closure glaucoma in people with narrow angles.
• Blood sugar. Weight loss can cause low blood sugar in people taking insulin or sulfonylureas.
• Alcohol. The label advises minimizing or avoiding it.

If you stop

What happens when you stop

Contrave does not cause the kind of withdrawal that opioids do, but weight tends to come back when any weight medicine stops. There is no trial of switching to Contrave after a GLP-1, so it cannot be promised to hold weight. In the semaglutide STEP 1 extension of 327 people, about two-thirds of lost weight returned within a year of stopping. Our posts on stopping Ozempic without regaining and maintenance after goal weight explain what a physician looks at.

Summit’s role

Summit’s role with naltrexone

Naltrexone and Contrave are not among the medicines Summit’s programs are built around, and I cannot confirm from Summit’s documents that Summit prescribes them. Summit does not dispense brand-name Contrave. Dr. Miranda reviews the medicines you already take and decides whether any add-on fits you after your history and labs. If you already take naltrexone or Contrave from another prescriber, say so on your application.

Summit is telehealth only. A physician decides, and some people will be told this medicine is not a fit. That is a normal outcome of a review.

Keep reading

Related medications

Sources

Where this comes from

All retrieved November 10, 2026.

1. Contrave (naltrexone HCl and bupropion HCl) extended-release tablets, prescribing information. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=485ff360-32c8-11df-928b-0002a5d5c51b
2. Greenway FL et al. Effect of naltrexone plus bupropion on weight loss in overweight and obese adults (COR-I). Lancet 2010. https://europepmc.org/article/MED/20673995
3. Wadden TA et al. Weight loss with naltrexone SR/bupropion SR as an adjunct to behavior modification: the COR-BMOD trial. Obesity 2011. https://europepmc.org/article/MED/20559296
4. Hollander P et al. Effects of naltrexone SR/bupropion SR on body weight and glycemic parameters in overweight and obese patients with type 2 diabetes. Diabetes Care 2013. https://europepmc.org/article/MED/24144653
5. Pi-Sunyer X et al. Psychiatric adverse events and effects on mood with prolonged-release naltrexone/bupropion: a pooled analysis. Int J Obes 2019. https://europepmc.org/article/MED/30664661
6. Wilding JPH et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab 2022. https://europepmc.org/article/MED/35441470