Bupropion-Naltrexone vs Semaglutide for Weight Loss

Bupropion-naltrexone (Contrave) and semaglutide (Wegovy) are both FDA-approved for chronic weight management, but they produce very different results: semaglutide leads to about 15% body weight loss on average, while bupropion-naltrexone typically produces 5–9%. The drugs work through completely different mechanisms, carry different price tags, and suit different patients. Choosing between them is less about which is "better" in the abstract and more about your health history, how much weight you need to lose, and what you can actually afford.

This explainer draws on peer-reviewed research from four obesity medicine specialists listed in the Convene directory: Caroline Apovian, M.D., at Brigham and Women's Hospital, who co-led the pivotal COR-II phase 3 trial of naltrexone SR/bupropion SR and co-authored the Endocrine Society pharmacological obesity management guideline; Ildiko Lingvay, MD, at Parkland Health in Dallas, whose work on the STEP trial program established semaglutide's benchmark weight loss outcomes; Jonathan Purnell, MD, at OHSU Knight Cardiovascular Institute, whose research on ghrelin physiology explains why these two drugs act on hunger through distinct neurobiological pathways; and Amy Rothberg, MD, at Michigan Medicine, whose clinical research covers intensive weight management and the practical factors that shape medication selection.

How each drug works

Bupropion-naltrexone combines two medications that have been used separately for years. Bupropion is a dopamine and norepinephrine reuptake inhibitor originally approved for depression and smoking cessation. Naltrexone is an opioid receptor antagonist used for alcohol and opioid use disorders. Together, they act on the hypothalamic pathways that regulate appetite and reward-driven eating. Bupropion stimulates neurons that suppress hunger, and naltrexone blocks the opioid feedback loop that would normally dampen that effect. The combination keeps the appetite-suppressing signal running longer than either drug can manage alone.

Semaglutide is a GLP-1 receptor agonist, a class that mimics glucagon-like peptide-1, a hormone released after eating. By activating GLP-1 receptors in the brain and gut, semaglutide slows gastric emptying, lowers glucagon, and sends sustained satiety signals to the hypothalamus. The result is a durable reduction in appetite and caloric intake that is substantially stronger than anything produced by the older centrally-acting drug combinations.

Jonathan Purnell, MD, whose research at OHSU established that ghrelin levels rise predictably before meals and after diet-induced weight loss, has helped explain why appetite suppression is so difficult to sustain with lifestyle interventions alone [8, 9]. When the body loses weight, ghrelin rises as a physiological counterregulation, pushing hunger back up. Both drug classes try to override that signal, but they do so through different receptors and with different potency.

What the clinical trials showed

The COR-II trial, a phase 3 randomized controlled trial co-led by Caroline Apovian, M.D., enrolled patients with overweight or obesity and tested sustained-release naltrexone 32 mg plus sustained-release bupropion 360 mg against placebo over 56 weeks [1]. On treatment, participants lost significantly more weight than those on placebo, and the drug improved lipid profiles and other cardiometabolic markers alongside the weight reduction. The average weight loss with bupropion-naltrexone was roughly 5–9% of body weight, depending on the endpoint analyzed.

The STEP 1 trial, a large randomized controlled trial published in the New England Journal of Medicine in 2021, tested weekly subcutaneous semaglutide 2.4 mg against placebo in adults with obesity or overweight without diabetes [4]. Participants lost a mean of about 15% of body weight over 68 weeks, compared to roughly 2.4% in the placebo group. Importantly, semaglutide also improved waist circumference, blood pressure, and lipid levels. For patients with obesity and type 2 diabetes, the STEP 2 trial published the same year showed a mean weight loss of around 10% with semaglutide 2.4 mg — less than in STEP 1, but still substantially more than bupropion-naltrexone achieves in comparable populations [6].

The gap between the two drugs grows wider when you look at the proportion of patients achieving meaningful thresholds. In the STEP 1 trial, 69% of semaglutide patients lost 10% or more of body weight. That kind of result is uncommon with bupropion-naltrexone.

What happens when you stop

One of the most important findings from the semaglutide trials is what happens after the drug is discontinued. The STEP 1 extension study, which followed patients for one year after stopping semaglutide, found that participants regained roughly two thirds of their prior weight loss and that cardiometabolic improvements largely reversed [7]. This pattern has confirmed for many endocrinologists that obesity is a chronic condition requiring ongoing treatment, not a short course that resets the body's set point.

Bupropion-naltrexone has a similar dynamic. Stopping the medication tends to be followed by weight regain, though the extension data for this drug is less extensive than for semaglutide.

Cardiovascular outcomes

A key distinction between these two drugs involves cardiovascular safety and benefit. Semaglutide has now demonstrated a reduction in major cardiovascular events in patients with obesity and established cardiovascular disease. The SELECT trial, published in the New England Journal of Medicine in 2023, enrolled over 17,000 patients with preexisting cardiovascular disease and obesity but without diabetes [5]. Over a mean follow-up of nearly 40 months, semaglutide reduced the combined endpoint of cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke compared to placebo. This makes semaglutide unusual among weight loss medications — it is the first in its class to show mortality-relevant cardiovascular benefit beyond weight loss alone.

Bupropion-naltrexone has a more complicated cardiovascular history. An early post-marketing cardiovascular outcomes trial was discontinued after concerns about interim data access, and the drug's FDA label carries a note that its cardiovascular effects have not been established in a completed outcomes trial. Patients with recent cardiovascular events or uncontrolled hypertension are generally not candidates for this drug.

At a glance

Who tends to do better on each

The Endocrine Society clinical practice guideline co-authored by Caroline Apovian, M.D., published in the Journal of Clinical Endocrinology & Metabolism, places both drug classes as options for patients who have not achieved adequate weight loss through lifestyle changes alone [2]. The 2013 AHA/ACC/TOS obesity management guideline, which she also co-authored, emphasizes that pharmacotherapy should be selected based on individual patient factors including comorbidities, contraindications, and treatment goals [3].

Semaglutide is often the preferred first choice when:

• You have a larger amount of weight to lose and need to reach a threshold (for example, before bariatric surgery, or to meaningfully improve a comorbidity like sleep apnea or joint pain)
• You have established cardiovascular disease or high cardiovascular risk
• You have type 2 diabetes alongside obesity (semaglutide improves glycemic control as well)
• Prior medications in the bupropion-naltrexone class have failed

Bupropion-naltrexone is often considered when:

• Cost is a major barrier and the significantly lower price of this oral medication matters
• You have a history of depression or are currently taking bupropion for another indication (though dose adjustments apply and this requires careful coordination)
• Injections are not acceptable or feasible
• Your weight loss target is modest and the 5–9% range would achieve your clinical goal

Bupropion-naltrexone is not appropriate if you have a seizure disorder, are using opioids for any reason (including pain management), have a history of bulimia or anorexia nervosa, or have uncontrolled hypertension.

The role of lifestyle and intensive behavioral treatment

Amy Rothberg, MD, at Michigan Medicine, whose clinical research on intensive meal replacement programs shows that behavioral and dietary intervention can produce substantial short-term weight loss [10], notes that medications work best alongside structured lifestyle change. In the clinical trials for both drugs, all participants received behavioral counseling alongside medication, and outcomes in real-world settings tend to be lower than trial results when that support is absent.

The point matters practically: neither drug is a substitute for changes in diet and activity. Both work by reducing appetite, which makes it easier to eat less — but you still have to eat differently.

Questions to ask your doctor

• Given my cardiovascular history, is one medication safer for me than the other?
• Do I have any contraindications to bupropion-naltrexone (seizures, opioid use, eating disorder history)?
• How much weight would I need to lose to improve my main health concern, and which drug is more likely to get me there?
• What does my insurance cover, and what is my realistic out-of-pocket cost for each option?
• If I need to stop the medication at some point, what is the plan for maintaining weight loss?
• Should I also be working with a registered dietitian or behavioral health provider alongside medication?

The bottom line

Semaglutide produces substantially greater weight loss than bupropion-naltrexone — about twice as much on average — and has now shown a reduction in serious cardiovascular events in patients with established cardiovascular disease. Bupropion-naltrexone is a reasonable option for patients with a more modest weight loss target, those who cannot afford or tolerate weekly injections, or those with specific clinical circumstances where GLP-1 receptor agonists are contraindicated. Both drugs require ongoing use to maintain their effects, and both work best alongside structured behavioral support.