Mysimba Weight Loss: How It Works, Side Effects, & More
Key Takeaways:
Mysimba® is a weight loss medicine that can help people with overweight or obesity lose weight.
Mysimba works by reducing appetite and curbing food cravings, helping you eat nutritious foods and proper portion sizes.
On Mysimba, you might lose about 11 percent of your body weight in a year.
Side effects include nausea, vomiting, and constipation.
Mysimba (naltrexone-bupropion) is a medication licensed in the United Kingdom to help adults with overweight or obesity lose weight.
If you’re considering the medicine, you’ve no doubt got questions. Below, we’ve got answers. We’ll cover how Mysimba works, side effects, and how you can get a prescription for Mysimba weight loss treatment.
What Is Mysimba?
Mysimba is a medicine that can help people with overweight or obesity lose weight. You take it as tablets twice a day, morning and evening.
A general practitioner (GP) or private clinician may prescribe Mysimba for weight loss if you have a body mass index (BMI) of 30 or more, or 27 or more with a weight-related health condition.
Those weight-related health conditions include:
Controlled high blood pressure (hypertension)
Type 2 diabetes
High cholesterol (dyslipidaemia)
Mysimba is prescribed alongside eating healthy foods and doing more movement as part of a treatment plan to promote weight loss.
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How Does Mysimba Work?
Mysimba works by suppressing your appetite. This helps you stick to nutritious foods and the right portion sizes for you, promoting weight loss.
Mysimba contains two active ingredients — naltrexone and bupropion.
Naltrexone is an opioid-receptor antagonist. It’s used to prevent relapse in people with opioid or alcohol dependence issues. Bupropion can help people stop smoking.
When combined, naltrexone and bupropion in Mysimba act on parts of the brain to suppress appetite and potentially curb food cravings, helping you avoid overeating.
How Effective Is Mysimba for Weight Loss?
Mysimba can be effective for weight loss.
In clinical trials, participants who took Mysimba for 56 weeks lost an average of 5.4 percent of their body weight. While taking the medicine, participants were encouraged to make lifestyle changes, like eating a reduced-calorie diet and doing more movement.
In another study on people taking Mysimba for 56 weeks, participants lost an average of 8.1 percent of their body weight. These participants had intensive behavioural modification counselling to help them build healthy lifestyle habits.
Some people respond better to Mysimba than others. Some participants in these trials lost an average of 11.3 percent of their starting body weight on Mysimba after a year.
Alongside promoting weight loss, Mysimba clinical trials show the medicine can:
Reduce waist circumference
Improve cholesterol levels
Reduce body fat — including visceral fat (fat that sits around your organs)
Improve insulin resistance in people without type 2 diabetes
Improve blood sugar control (glycaemic control) in people with type 2 diabetes
Ask your GP if they think Mysimba might help you lose and maintain weight based on your health history.
How Long Does Mysimba Take to Work?
Mysimba starts working in your body right away. But it can take some time before you feel the effects on your appetite and see a difference in your weight.
Some participants taking Mysimba report weight loss by the 4-week mark, so you may see some progress within your first month on the medicine.
If you haven’t lost at least 5 percent of your starting weight after 16 weeks, let your GP or private healthcare professional know. They might recommend you stop taking the medicine and try an alternative weight loss treatment instead.
How to Take Mysimba
Your GP or private clinician will let you know how to take Mysimba. Always follow their instructions based on your personal circumstances and medical history.
Mysimba is typically taken as daily tablets. Swallow the tablet whole with water, and ideally with food. Don’t crush, chew, or cut Mysimba tablets.
You’ll start on a low dose of Mysimba that gradually increases each week. Your dosing schedule could look like this.
Week of treatment
Dose
Week 1
1 tablet in the morning
Week 2
1 tablet in the morning + 1 tablet in the evening
Week 3
2 tablets in the morning + 1 tablet in the evening
Week 4 and beyond
2 tablets in the morning + 2 tablets in the evening
The maximum daily dose of Mysimba is 32 milligrams (mg) of naltrexone and 360 mg of bupropion in total across the day.
What Should I Do If I Miss a Dose of Mysimba?
If you miss a dose of Mysimba, let it go. Don’t take extra medicine to make up for the missed dose. Take your next dose of Mysimba at your usual time.
Mysimba Side Effects
Like any medicine, Mysimba comes with potential side effects.
The most common side effects of Mysimba are:
Nausea
Vomiting
Constipation
Dizziness
Headache
Dry mouth
Nausea, vomiting, and constipation tend to crop up in the first 4 weeks of treatment as your dose is increasing. These side effects should get better with time. In clinical trials, vomiting got better for many people within 1 week, and nausea improved within 4 weeks.
Heads-up: You might be more likely to get gastrointestinal side effects like these if you have type 2 diabetes.
There are also rare side effects of Mysimba, including:
Numbness and tingling (paraesthesia)
Abdominal pain
Irregular periods
Fainting
Hallucinations
Mysimba can also make you feel sleepy, so be careful when driving or operating heavy machinery. Avoid these activities if you feel extra drowsy or dizzy on Mysimba.
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Who Can’t Take Mysimba?
Mysimba isn’t right for everyone. For example, you can’t take the medicine if you have:
Uncontrolled high blood pressure
A seizure disorder or a history of seizures
A history of bipolar disorder
You also can’t take Mysimba if you’re pregnant, trying for a baby, or breastfeeding.
Mysimba interacts with some other medicines, like monoamine oxidase inhibitors (MAOIs) and opioid analgesics.
Let your GP or private prescriber know about any medical issues you have or other medications you’re taking. They can make sure Mysimba is right for you.
How to Get Mysimba
You can get Mysimba by connecting with a healthcare professional. They’ll most likely ask you about your weight, BMI, and medical history to determine if you’re eligible for Mysimba. If so, they’ll write you a prescription.
Can You Get Mysimba Online?
You can get Mysimba online through some telemedicine platforms. You’ll connect with a private clinician who can make sure Mysimba is right for you and write you a prescription if it is.
Can You Get Mysimba on the NHS?
Mysimba isn’t usually available on the National Health Service (NHS). You’ll probably need a private prescription to get Mysimba.
If you’re looking for weight loss treatments on the NHS, your GP might recommend weight loss injections or other weight loss tablets. There are usually strict eligibility criteria for who can get weight loss treatment on the NHS, as well as long waiting lists.
Mysimba Weight Loss Alternatives
Mysimba isn’t your only option for medicines to support your weight loss journey.
There are weight loss injections, including:
These weight loss injections work by reducing hunger and making you feel fuller for longer. Semaglutide and tirzepatide are weekly injections, and liraglutide is a once-daily injection.
Beyond Mysimba, there are other weight loss pills, like orlistat (Xenical®, Alli®, Orlos®).
Orlistat works by reducing how much fat your body absorbs from food. Xenical is available on prescription, and Alli and Orlos are available over the counter (OTC). They contain lower doses of orlistat than Xenical, and you take them under the supervision of a pharmacist.
A GP or private healthcare professional can help you find the best treatment options for you.
Medicine
Pill or injection
How often to take it
Mysimba
Pill
2x/day, morning and night
Wegovy®
Injection
1x/week
Mounjaro®
Injection
1x/week
Saxenda®
Injection
1x/day
Nevolat
Injection
1x/day
Xenical
Pill
3x/day before meals
Mysimba Weight Loss: Final Thoughts
For some, weight loss medicines are the missing piece of the puzzle when it comes to losing weight and improving health. Mysimba is one of those medicines.
Here are the key points:
Mysimba can reduce your appetite. It’s a pill you take twice a day. You may be eligible if you have a BMI of 30 or more, or 27 or more with a weight-related health condition.
Mysimba comes with side effects. It can cause nausea, constipation, vomiting, and headaches, especially at the start of treatment.
Other weight loss medicines are available. You may be eligible for weight loss injections, like semaglutide and tirzepatide, and other weight loss pills, like orlistat.
You can learn more about weight loss medications through the Hers U.K. platform.
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FAQs
Get answers to frequently asked questions about Mysimba weight loss treatment.
Can I drink alcohol on Mysimba?
You can technically drink alcohol on Mysimba, but you should limit how much you drink and potentially cut out alcohol altogether. Speak to your GP or private healthcare professional to find out whether it’s safe for you to drink alcohol on Mysimba.
What should I eat on Mysimba?
There isn’t a specific list of foods to eat on Mysimba. In general, you should eat nutritious, whole foods to promote healthy weight loss. These include:
Fruits and veg
Legumes, like lentils, beans, and chickpeas
Lean protein sources, like chicken, turkey, fish, and tofu
Whole grains, like brown rice, oats, and wholemeal bread
Is Mysimba safe?
Mysimba is safe for many people. The most common side effects are gastrointestinal, including nausea, vomiting, and constipation. These side effects tend to get better in a few weeks. Some people can’t take Mysimba. Your GP or private healthcare professional can determine if the medicine is safe for you.
Is Mysimba as good as Ozempic®?
In the U.K., Mysimba is a weight loss medicine, and Ozempic® is a type 2 diabetes medicine. Although Ozempic® can cause weight loss, healthcare professionals are encouraged not to prescribe it for weight loss alone. So, if you don’t have type 2 diabetes, Mysimba may be a better choice for you.
Can you get Mysimba over the counter?
No, you can’t get Mysimba over the counter. It’s only available on prescription, so a GP or private healthcare professional will need to determine that the medicine is right for you and write you a prescription for it if so.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.