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Mysimba vs Saxenda: A Comprehensive Comparison

Obesity is a long-standing health burden in the UK, and it is worsening. 25% of the adult population are deemed obese. To relieve some of the pressures on the NHS, there has been a steady increase in weight loss drugs approved for use depending on specific eligibility criteria.

Two examples of licensed weight loss medicines in the UK are Mysimba and Saxenda. Both medicines have shown potential benefits for weight loss but differ in drug class and how they work.

At a glance

  • Mysimba is taken by mouth via tablets whereas Saxenda is an injection under the skin (subcutaneous).
  • The dose is increased weekly for both medicines until an optimal dosage is reached weeks later.
  • Both medicines work differently for weight loss. Trial data suggests Saxenda results in a greater percentage of weight loss compared to Mysimba but also results in side effects.

Mysimba vs Saxenda: Active Ingredients and How They Work

The weight loss properties of these drugs rely on their active ingredients.

Mysimba is a combination of two drugs: naltrexone, an opioid antagonist (i.e. blocks the effects of the opioid receptors) and buproprion, a type of antidepressant. Saxenda only has one active ingredient: liraglutide, a glucagon-like peptide-1 (GLP-1) agonist.

Because these medicines are from different drug classes, they work differently too.

For Mysimba, it is a dual approach. Naltrexone blocks opioid receptors in the brain, potentially reducing appetite as the opioid receptors have a partial role in regulating hunger. Bupropion affects neurotransmitters (i.e. ‘brain chemicals’) like dopamine which can lead to feeling less hungry and more calories burned.

Liraglutide in Saxenda works quite differently. As a GLP-1 agonist, it mimics GLP-1 which regulates appetite. Like Mysimba, it also has dual effects. By delaying the duration which your stomach empties, you feel fuller for longer. It can also activate GLP-1 receptors in the brain which control hunger, causing less interest in eating and hence weight loss.

Dosage and Administration Differences between Mysimba and Saxenda

Both drugs have different doses because Mysimba is taken as tablets whereas Saxenda is given as an injection.

Mysimba’s dose increases gradually. You start with one tablet (8mg naltrexone/90mg bupropion) in the morning, and then the dose gradually increases over 4 weeks to two tablets twice a day (four tablets maximum daily dose). Ideally, take it with food.

11 tablet daily
21 tablet twice a day
32 tablets in the morning, 1 tablet in the evening
42 tablets in the morning, 2 tablets in the evening

Saxenda also requires a dose increase, gradually over 5 weeks. The first injection dose is 0.6mg daily for 1 week and then the dose increments increase by 0.6mg weekly. The maximum daily dose is 3mg.


Effectiveness of Mysimba and Saxenda for Weight Loss

Four clinical trials involving a total of 4500 overweight or obese patients compared the weight loss effects of Mysimba to a placebo drug. All participants were also enrolled in a weight loss program that included diet and exercise advice. The studies lasted either 28 or 56 weeks.

A summary of the findings from the European Medicines Agency concluded:

OutcomeMysimba (%)Placebo (%)Further details
Average weight loss3.7-5.71.3-1.9Across 3 studies
≥ 5% Weight loss28-4212-14Higher success rates with additional counselling
≥ 10% Weight loss13-225-6Higher success rates with additional counselling

The evidence behind Saxenda (liraglutide) for weight loss comes from the SCALE trial; a randomised control trial consisting of 3731 patients. In a 56-week double-blind trial, a 3mg daily dose of liraglutide was compared against a placebo drug, both alongside dietary advice and exercise. Randomised controlled trials are ‘high quality’ evidence because each patient has an equal chance of being assigned to either treatment therefore reducing bias.

Trial participants were adults who were obese (BMI ≥ 30) or overweight (BMI ≥ 27).

Key outcomes were as follows:

  • Patients taking liraglutide lost on average 8.4 kg, whereas average weight loss was 2.8 kg in the placebo group. The difference was -5.6kg.
  • 63.2% of patients who administered liraglutide lost at least 5% of their body weight versus 27.1% in the placebo group.
  • 33.1% of patients who administered liraglutide lost more than 10% of their body weight, versus 10.6% in the placebo group.
  • Mild to moderate nausea and diarrhoea were amongst the most common side effects of liraglutide. It is worth noting that the rate of serious events was 1.2 times higher in the liraglutide group (6.2%) versus the placebo group (5.0%).

 Both Mysimba and Saxenda taken with diet and exercise resulted in greater weight compared to placebo. It is difficult to make direct comparisons between the two treatments because the trials were different in multiple ways e.g. sample size, number of studies, methods used. There are no published trials directly comparing the two as yet.

Mysimba vs Saxenda Costs

A box of Mysimba contains 112 tablets and costs £109.99. This will last almost 6 weeks initially and then 28 days once the optimal dose is reached.

Saxenda injection pens come in pack sizes of 5 or 10. Each pen costs £59.79 in a pack of 5 or £55.99 each in a pack of 10. All orders include needles and a sharps bin to allow for safe injection. To reach the optimal dose of 3mg, this requires about 4 pens. Following this, each Saxenda pen (at the optimal dose of 3mg daily) will last 6 days.

Where can I buy Mysimba or Saxenda for weight loss?

Unfortunately, Saxenda is discontinued but Mysimba is a viable alternative which can be bought online from Prescription Doctor.

Before purchase, you will take part in a short online consultation which consists of an online medical questionnaire. This is to help our clinicians determine if these weight loss medicines are best suited for you or if other treatments are more appropriate. You must meet the eligibility criteria to qualify for Mysimba weight loss treatment.

If our clinicians decide your chosen treatment is not suitable, you will receive a full refund as part of our money-back guarantee.

Which drug is best for you?

Each of us is different, and the drug which suits you the best depends on many factors, not just efficacy. These include:

  • Route of administration: Mysimba may be more convenient as it is given as tablets and you may not like injections (e.g. pain).
  • Cost: At optimal dosage, Mysimba is less costly compared to Saxenda.
  • Side effects: The trials show that more serious effects occurred with Saxenda compared to placebo.


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From research, it seems that Saxenda may result in greater weight loss compared to Mysimba but at a greater risk of side effects. As the medicines were compared to placebos rather than direct comparison, there is no evidence to suggest that Saxenda is more effective than Mysimba.

The evidence suggests either of these medicines can be an effective supplement to help you lose weight, with optimal results incorporating lifestyle changes such as dietary plans and exercise.

Our clinicians can support you on your weight loss journey to determine and recommend the best medicine for you. We also offer a wide range of alternative weight loss medicines such as Wegovy and Mounjaro.


Medicines, 2023. Mysimba 8 mg/90 mg Product Information

European Medicines Agency, 2015. Mysimba: EPAR - Product Information.

NHS, 2021. Obesity.

NICE, 2020. Naltrexone with Bupropion.

Authored & Reviewed By

Mohamed Imran Lakhi

MPharm - Lead Pharmacist
Imran Lakhi is the superintendent pharmacist and founder at Prescription Doctor. He has been at the core of our team.

Published on: 13/06/2024 Reviewed on: 13/06/2024
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