How To Use Mysimba
Complete Step-by-Step Usage Guide, Dosage Instructions & Safety Information
Table of Contents
- Key Takeaways
- How to Take Mysimba: Step‑by‑Step Usage Guide
- Mysimba Dosage Guide: Starting and Maintenance Doses
- Who Should Use Mysimba? (Indications)
- Who Should NOT Use Mysimba? (Contraindications)
- Should Mysimba Be Taken with Food or Without Food?
- Special Conditions: Pregnancy, Breastfeeding, Liver/Kidney Issues
- Mysimba Usage FAQs
Key Takeaways: How to Use Mysimba Correctly
- Dose escalation: Start with one tablet daily, increase gradually over 4 weeks to reach maintenance dose (two tablets twice daily).
- Take with food: Always swallow tablets whole with food to reduce nausea and improve tolerability.
- Do not crush or chew: Prolonged-release tablets must be swallowed whole.
- Consistent timing: Take doses at the same times each day (morning and evening).
- 16‑week review: Your doctor will check if you’ve lost at least 5% of your starting weight; if not, treatment may be stopped.
- Avoid opioids: Mysimba contains naltrexone which blocks opioids – do not use opioid‑containing medicines.
Mysimba is a prescription‑only weight management medicine that must be used exactly as directed by your doctor. Following the correct dosing schedule and administration guidelines ensures the best results while minimising side effects. Always combine Mysimba with a reduced‑calorie diet and increased physical activity.
Important Medical Advice
If you experience suicidal thoughts, seizures, swelling of the face/lips/tongue (angioedema), or signs of an allergic reaction, stop Mysimba and seek immediate medical help. Do not take Mysimba if you are using opioids or within 14 days of stopping MAO inhibitors. If you miss a dose, skip it – never double dose.
How to Take Mysimba: Step‑by‑Step Usage Guide
Mysimba tablets are designed to be taken twice daily following a gradual dose escalation schedule. This helps your body adjust to the medicine and reduces the chance of side effects like nausea and headache.
Step‑by‑Step Administration
- Check the dose: Follow the 4‑week escalation plan provided by your doctor (see dosage guide below).
- Take with food: Swallow tablets whole with a glass of water during or immediately after a meal.
- Morning dose: Take the morning dose soon after breakfast.
- Evening dose: Take the evening dose soon after your evening meal (at least 8 hours after the morning dose).
- Do not crush or chew: The tablets are prolonged‑release; breaking them can cause a dangerous rapid release of the medicine.
- Stay consistent: Try to take your doses at the same times each day to maintain steady levels in your body.
🗒️ Practical tip: If you forget a dose, skip it and take the next dose at the usual time. Never take two doses at once to make up for a forgotten dose.
Mysimba Dosage Guide: Starting and Maintenance Doses
The recommended dosing schedule is the same for all patients, unless your doctor advises otherwise due to kidney or liver problems. Do not exceed 4 tablets per day.
| Week | Morning dose | Evening dose | Total daily tablets |
|---|---|---|---|
| Week 1 | 1 tablet | 0 | 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 |
Important dosing rules
- Each tablet contains 8 mg naltrexone hydrochloride and 90 mg bupropion hydrochloride.
- The maintenance dose is two tablets twice daily (total of 4 tablets per day).
- If you miss several days, do not restart at the maintenance dose – begin again at week 1 and escalate gradually.
- Your doctor will reassess your progress after 16 weeks. If you haven’t lost at least 5% of your initial body weight, Mysimba should be stopped.
Who Should Use Mysimba? (Indications)
Mysimba is prescribed for adults (18 years and older) who meet specific body mass index (BMI) criteria and have been unable to lose weight through diet and exercise alone.
Approved patient groups
- Obesity: BMI of 30 kg/m² or higher.
- Overweight with comorbidity: BMI between 27 and 30 kg/m² AND at least one weight‑related condition such as:
- Type 2 diabetes
- Controlled high blood pressure (hypertension)
- Abnormal lipid levels (dyslipidaemia)
Mysimba should only be used as part of a comprehensive weight management plan that includes a reduced‑calorie diet and increased physical activity. Your doctor will confirm your eligibility and may perform blood tests before starting treatment.
Who Should NOT Use Mysimba? (Contraindications)
Mysimba is not suitable for everyone. Do not take Mysimba if any of the following apply to you:
Allergy
Allergic to naltrexone, bupropion, or any tablet ingredients.
Uncontrolled high blood pressure
Hypertension that is not well managed with medication.
Seizure disorders
Epilepsy or a history of seizures (fits).
Eating disorders
Current or past bulimia or anorexia nervosa.
Opioid dependence
Current opioid use, opioid addiction, or acute opioid withdrawal.
MAO inhibitors
Taking MAOIs (for depression or Parkinson’s) or within the last 14 days.
Severe liver disease
End‑stage liver disease or severe hepatic impairment.
End‑stage kidney disease
Severe renal impairment requiring dialysis.
Bipolar disorder
History of manic episodes or bipolar illness.
Brain tumour
Active brain tumour or central nervous system condition.
Also, Mysimba should not be used during pregnancy or breastfeeding (see special conditions). Always inform your doctor about your full medical history.
Should Mysimba Be Taken with Food or Without Food?
Always take Mysimba with food. Taking it with a meal (breakfast and evening meal) helps reduce common side effects like nausea and also improves how well the medicine is tolerated.
Why take with food?
- Reduces nausea: Food buffers the stomach and decreases the likelihood of gastrointestinal upset.
- Steadies absorption: While a high‑fat meal can slightly increase peak levels, taking it consistently with meals provides stable blood concentrations.
- Improves adherence: Linking doses to meals makes it easier to remember.
What to avoid
Do not take Mysimba with alcohol. Excessive alcohol use while on Mysimba may increase the risk of seizures. Also, avoid grapefruit juice as it may affect bupropion metabolism.
🗒️ Food tip: If you experience nausea, try taking the tablets in the middle of a meal rather than at the end. If nausea persists, contact your doctor – they may adjust your dose or suggest anti‑nausea measures.
Special Conditions: Pregnancy, Breastfeeding, Liver/Kidney Issues
Pregnancy
Do not use Mysimba during pregnancy. There is limited data on safety, and weight loss during pregnancy is not recommended. If you become pregnant while taking Mysimba, stop the medicine immediately and inform your doctor. Women of childbearing age should use effective contraception during treatment.
Breastfeeding
Mysimba passes into breast milk and may harm the nursing infant. Breastfeeding is not recommended while taking Mysimba, and for 5 days after the last dose (due to bupropion’s long half‑life).
Liver problems
- Mild to moderate liver impairment: Use with caution; your doctor may monitor you more closely. Dose adjustment may be needed.
- Severe liver disease: Mysimba is contraindicated (do not use).
Kidney problems
- Mild to moderate kidney impairment: No dose adjustment usually required, but caution advised.
- End‑stage kidney disease: Mysimba is contraindicated (do not use).
Elderly (≥65 years)
Mysimba can be used, but with caution. It is not recommended for people over 75 due to lack of data.
Children and adolescents
Mysimba is not approved for anyone under 18 years of age.
Mysimba Usage FAQs
What should I do if I miss a dose of Mysimba?
Skip the missed dose and take your next dose at the regular time. Never double up. If you miss several days, contact your doctor for advice on restarting.
Can I cut or crush Mysimba tablets?
No. Mysimba tablets are prolonged‑release and must be swallowed whole. Cutting or crushing can release the medicine too quickly, increasing the risk of seizures and side effects.
How long does it take for Mysimba to start working?
Appetite suppression may begin within the first few weeks, but full effect is assessed at 16 weeks. You should aim to lose at least 5% of your starting weight by then.
Can I drink alcohol while taking Mysimba?
It's best to avoid alcohol. Excessive drinking increases the risk of seizures and may worsen side effects like dizziness. If you drink heavily, do not stop suddenly without medical advice.
Is Mysimba safe to take with other medicines?
Mysimba can interact with many drugs, including antidepressants, opioids, and blood pressure medications. Always provide your doctor with a full list of your current medicines.
Ready to Start Your Weight Management Journey?
If Mysimba sounds like the right option for you, speak with a UK‑registered doctor through a confidential online consultation. They will check your suitability and provide a prescription if appropriate.
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Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 22 February 2026
Next Review: 22 August 2026
Published on: 22 February 2026
Last Updated: 22 February 2026