What is Mysimba?
Mysimba is a prescription weight-management medicine containing two active ingredients: naltrexone and bupropion, in prolonged-release tablets. It is approved by the European Medicines Agency (EMA) for weight management in adults, used as an adjunct to a reduced-calorie diet and increased physical activity.
Mysimba is indicated for adults with an initial body mass index (BMI) of 30 or above (obese), or a BMI of 27 to below 30 (overweight) in the presence of one or more weight-related comorbidities, such as type 2 diabetes, dyslipidaemia, or controlled hypertension.
How does Mysimba work?
Mysimba combines two medicines that act on the central nervous system pathways regulating appetite and food reward:
- Naltrexone is an opioid receptor antagonist. It blocks signals in the brain’s reward system that make food — particularly highly palatable food — feel satisfying, helping to reduce cravings and binge-type eating.
- Bupropion is a norepinephrine-dopamine reuptake inhibitor. It increases the activity of these neurotransmitters in the hypothalamus, reducing hunger and supporting energy balance.
Together, these actions help reduce appetite and food cravings, making it easier to follow a reduced-calorie diet. Mysimba is not a stimulant and is not related to GLP-1 medicines such as semaglutide.
Who is Mysimba for?
Mysimba may be considered for adults aged 18 and over who have:
- A BMI of 30 or above, or
- A BMI of 27 or above with at least one weight-related condition such as type 2 diabetes, dyslipidaemia (high cholesterol), or controlled hypertension
Mysimba is not suitable for everyone. It must not be used by people who:
- Use opioid medicines or are dependent on opioids
- Are in acute opioid withdrawal or receive opioid-agonist treatment
- Take another medicine containing naltrexone or bupropion
- Have uncontrolled high blood pressure
- Have current or previous seizures
- Have a central nervous system tumour
- Are in acute withdrawal from alcohol, benzodiazepines, or other sedatives
- Have severe liver or kidney problems
- Have a history of bipolar disorder
- Are pregnant or breastfeeding
- Have taken an MAO inhibitor antidepressant in the last 14 days
- Have current or previous bulimia or anorexia
- Are allergic to any Mysimba ingredient
A full medical assessment by a qualified, independent doctor is required before any prescription can be issued.
Dosage
Mysimba is a daily oral tablet taken with food and swallowed whole. The dose increases gradually over four weeks to improve tolerability:
| Week | Morning | Evening | Total daily dose |
|---|---|---|---|
| Week 1 | 1 tablet | — | 1 tablet |
| Week 2 | 1 tablet | 1 tablet | 2 tablets |
| Week 3 | 2 tablets | 1 tablet | 3 tablets |
| Week 4 onwards | 2 tablets | 2 tablets | 4 tablets |
The maximum dose is 4 tablets per day, equivalent to 32 mg naltrexone and 360 mg bupropion. Do not adjust your dose without consulting your prescribing doctor.
If at least 5% of starting body weight has not been lost after 16 weeks of treatment, the prescriber should discontinue Mysimba. At least once a year, a doctor must reassess benefit and cardiovascular risk. Because cardiovascular safety beyond 12 months remains uncertain, the prescriber should discontinue after one year if at least 5% weight loss from starting body weight has not been maintained.
Side effects
As with all medicines, Mysimba may cause side effects. Not everyone experiences them, and many become milder as the body adapts.
Common side effects
- Nausea (most common, especially in the first weeks)
- Constipation
- Vomiting
- Headache
- Dry mouth
- Dizziness
- Insomnia
- Anxiety
- Increased blood pressure and heart rate
Taking Mysimba with food and following the gradual dose schedule helps reduce nausea. Blood pressure and heart rate should be monitored during treatment.
Serious side effects
- Seizures: Bupropion can lower the seizure threshold. Seek immediate medical attention if you experience a seizure.
- Hypertensive reactions: Report severe headache, vision changes, or chest pain to a doctor promptly.
- Mood changes: Bupropion carries a warning for depression and suicidal thoughts in some people. Contact a doctor immediately if you experience mood deterioration, agitation, or unusual thoughts.
If you take opioid medicines, naltrexone can suddenly trigger withdrawal and block pain relief — this is why opioid use is a strict contraindication.
Important safety and follow-up
Mysimba must not be used by people with allergy to its ingredients; uncontrolled hypertension; current or previous seizures; a central nervous system tumour; acute withdrawal from alcohol, benzodiazepines or other sedatives; a history of bipolar disorder; current treatment with another medicine containing bupropion or naltrexone; current or previous bulimia or anorexia; current opioid use, opioid dependence, opioid agonist treatment or acute opioid withdrawal; MAOI use within the last 14 days; pregnancy or breastfeeding; or severe liver or kidney impairment.
Tell the independent doctor about every opioid-containing medicine, including pain, surgery, cough, cold or diarrhoea products. Naltrexone can precipitate withdrawal and block opioid pain relief. Tell the doctor and surgical team well before any planned surgery or possible need for opioid pain relief; do not start, stop or interrupt Mysimba yourself.
At least once a year, a doctor must reassess the treatment benefit and cardiovascular risk. Cardiovascular safety beyond 12 months remains uncertain. The prescriber should discontinue after one year if at least 5% weight loss from starting body weight has not been maintained.
Mysimba vs other weight-management options
| Medicine | Active ingredient | Form | Typical use |
|---|---|---|---|
| Mysimba | Naltrexone/bupropion | Daily oral tablet | Weight management (EU-approved) |
| Xenical | Orlistat | Daily oral capsule | Blocks fat absorption |
| Ozempic / Wegovy | Semaglutide | Weekly injection | GLP-1 therapy; diabetes and weight management |
| Tenuate Retard | Amfepramone | Daily oral capsule | Short-term appetite suppression |
Which option is appropriate depends on your medical history, current medicines, and treatment goals. An independent doctor makes this decision during the assessment — Prescrivia does not influence or guarantee prescribing outcomes.
How to access Mysimba online in Europe
Mysimba is a prescription-only medicine in all EU member states. Prescrivia is a technology intermediary — we do not prescribe medicines, employ doctors, or sell medicines. Our platform connects patients with independent EU-registered doctors:
- Complete an online assessment: Answer questions about your height, weight, medical history, and current medicines.
- Doctor review: An independent, EU-registered doctor reviews your assessment. If Mysimba is clinically appropriate, they may issue a prescription; if not, they will explain why and may suggest alternatives.
- Pharmacy dispensing: Prescribed medicines are dispensed and shipped by licensed EU pharmacies.
Sources
- European Medicines Agency (EMA). Mysimba (naltrexone/bupropion) — Summary of Product Characteristics. Available at: ema.europa.eu
- EMA EPAR: Mysimba, EMEA/H/C/003687.
How can we help you?
- What is Mysimba used for?
- Mysimba contains naltrexone and bupropion and is approved by the European Medicines Agency for weight management in adults. It is used alongside a reduced-calorie diet and increased physical activity in adults with a BMI of 30 or above, or a BMI of 27 or above with a weight-related condition such as type 2 diabetes, dyslipidaemia, or controlled hypertension.
- Can I get Mysimba online in Europe?
- Yes. Mysimba is a prescription-only medicine in EU member states. Through Prescrivia you can complete a confidential online health assessment, which is reviewed by an independent, EU-registered doctor who decides whether Mysimba is clinically appropriate for you.
- How is Mysimba different from Ozempic or Xenical?
- Mysimba is a daily oral tablet that acts on brain pathways controlling appetite and food reward. Ozempic (semaglutide) is a weekly injection that mimics the GLP-1 hormone, and Xenical (orlistat) blocks fat absorption in the gut. They have different mechanisms, side-effect profiles, and suitability, which a doctor considers during assessment.
- How long do I take Mysimba?
- Treatment starts with a low dose that increases over four weeks. If at least 5% of starting body weight has not been lost after 16 weeks, the prescriber should discontinue treatment. At least once a year, a doctor must reassess benefit and cardiovascular risk; the prescriber should discontinue after one year if at least 5% weight loss has not been maintained.
Related treatments
Compare related options in the same wider treatment route.
Intermediary notice: Prescrivia connects patients with independent EU-registered doctors and licensed pharmacies. We do not provide medical advice, employ doctors, or sell medicines directly. All medical decisions are made by independent healthcare professionals, and prescription-only medicines require a valid prescription. Treatment is not guaranteed — whether a prescription is issued depends on an independent doctor's clinical assessment.