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Mysimba

  • Weight-loss medicine
  • BMI of 27 kg/m² or greater
  • Avoid drinking alcohol while taking this medicine
  • Can cause dizziness

About Mysimba

Mysimba contains two active ingredients, naltrexone hydrochloride and bupropion hydrochloride, and is used in obese or overweight adults to manage weight together with a reduced calorie diet and physical exercise.

This medicine works on areas on the brain involved in the control of food intake and energy expenditure.

Obesity in adults over 18 years of age is defined as a body mass index (BMI) of greater than or equal to 30 and overweight in adults over 18 years of age is defined as a BMI of greater than or equal to 27. The body mass index is calculated as the measured body weight (kg) divided by the measured height squared (m2).


Mysimba is approved for use in patients with an initial BMI of 30 or greater. It can also be given to those with a BMI of between 27 and 30 if they have additional weight-related conditions such as controlled high blood pressure (hypertension), type 2 diabetes or high levels of lipid (fat) in the blood.

Mysimba may be discontinued by your doctor after 16 weeks if you have not lost at least 5 percent of your initial body weight. Your doctor may also recommend stopping treatment if there are concerns about increased blood pressure, or other concerns with the safety or tolerability of this medicine.

How to take Mysimba

Always take this medicine exactly as your doctor has told you. Check with your doctor or pharmacist if you are not sure.

The initial dose is usually:

  • one tablet (8 mg naltrexone hydrochloride / 90 mg bupropion hydrochloride) once a day in the morning.

The dose will be gradually adapted as follows:

  • Week 1: one tablet once a day in the morning.
  • Week 2: two tablets every day, one in the morning and one in the evening.
  • Week 3: three tablets every day, two in the morning and one in the evening.
  • Week 4 and onward: four tablets every day, two in the morning and two in the evening.

The maximum recommended daily dose of Mysimba is four tablets (two tablets taken twice a day).

This medicine is for oral use. Swallow your tablets whole. Do not cut them, chew them or crush them. The tablets should preferably be taken with food.

After 16 weeks and each year after your treatment initiation, your doctor will evaluate whether you

should continue to take Mysimba.

Driving/alcohol

Mysimba can cause dizziness. Do not drive, use any tools or machines, or perform dangerous activities until you know how this medicine affects you.

Excessive use of alcohol while being treated with Mysimba might increase the risk for fits (seizures),

mental disorder events or might reduce alcohol tolerance. Your doctor may suggest you do not drink alcohol while you are taking Mysimba, or try to drink as little as possible. If you do drink a lot now, do not just stop suddenly, because that may put you at risk of having a fit.

If you take more or less Mysimba than you should/stop taking Mysimba

If you take too many tablets, you may be more likely to have side effects. Do not delay, contact your doctor or your nearest hospital emergency department immediately.

If you forget to take a dose of Mysimba, then skip the missed dose and take your next dose at the next usual time. Do not take a double dose to make up for a forgotten dose.

You may need to take Mysimba for at least 16 weeks to have its full effect. Do not stop taking Mysimba without talking to your doctor first.

When not to use Mysimba

Mysimba is not suitable for everyone. Do not take Mysimba if:

  • You are allergic to any of the ingredients in this medicine (see section ‘What Mysimba contains').
  • You have an abnormally high blood pressure (hypertension) that is not controlled using a
  • medicinal product.
  • You have a condition that causes fits (seizures) or if you have a history of fits.
  • You have a brain tumour.
  • You are usually a heavy drinker and you have just stopped drinking alcohol, or are going to stop while you are taking Mysimba.
  • You have recently stopped taking sedatives or medicines to treat anxiety (especially
  • benzodiazepines), or if you are going to stop them while you are taking Mysimba.
  • You have or have had a bipolar disorder (extreme mood swings).
  • You are using any other medicines which contain bupropion or naltrexone.
  • You have an eating disorder or had one in the past (for example, bulimia or anorexia nervosa).
  • You are currently dependent on chronic opiates or opiate agonists (for example methadone), or you are going through acute withdrawal (cold turkey).
  • You are taking medicines for depression or Parkinson’s disease called monoamine oxidase
  • inhibitors (MAOIs) or have taken them in the last 14 days.
  • You have severe liver disease.
  • You have endstage kidney disease.

This medicine is not suitable for use in children.

When should this medicine be used with caution?
Talk to your doctor or pharmacist before taking this medicine if:

  • You feel depressed, contemplate suicide, have a history of attempting suicide or any other mental health problems.
  • You are taking medicines that may increase the risk of fits (see 'Other medicines and Mysimba').
  • You have high blood pressure before taking Mysimba.
  • You have uncontrolled coronary artery disease (a heart disease caused by poor blood flow in the blood vessels of the heart) with symptoms such as angina (characterised by chest pain) or a recent heart attack.
  • You already have or have had a condition affecting the circulation of blood in the brain
  • (cerebrovascular disease).
  • You have any liver or kidney problems before you start Mysimba.
  • You have a history of mania (feeling elated or over-excited, which causes unusual behaviour).
  • You are 65 years or older.

Pregnancy and breastfeeding

Mysimba should not be used during pregnancy or while breastfeeding.

Other medicines and Mysimba

Mysimba may interact with other medicines.

Do NOT take Mysimba with:

  • Monoamine oxidase inhibitors. You must stop taking these medicines for at least 14 days before starting Mysimba.
  • Opiates and opiate-containing medicines for example to treat cough and cold, opiate addiction, pain, and diarrhoea. You must have stopped taking any opiate medicines at least 7-10 days before starting Mysimba.

Tell your doctor if you are taking any of the following medicines, as your doctor will closely monitor you for side effects:

Medicines that may, when used alone or in combination with naltrexone/bupropion, increase the risk of fits.
Medicines for depression and other mental health problems.
Some medicines used to treat high blood pressure.
Some medicines used to treat irregular heart rhythm.
Some medicines used to treat cancer.
Some medicines for Parkinson’s disease.
Ticlopidine or clopidogrel, mainly used in the treatment of heart disease or stroke.
Medicines used in the treatment of HIV infection and AIDS.
Medicines used to treat epilepsy.
For a complete list of warnings, see the package leaflet.

Side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them.

Serious side effects

  • Fits (seizures). Rare - may affect up to 1 in 1,000 people taking Mysimba with a risk of having a fit.

Very common side effects (may affect more than 1 in 10 people)

  • Nausea and/or vomiting.
  • Stomach pain.
  • Constipation.
  • Headache.
  • Difficulty sleeping (make sure you do not take Mysimba near to bedtime).
  • Anxiety.
  • Pain in the joints or in the muscles.

Common side effects (may affect up to 1 in 10 people)

  • Low number of white blood cells.
  • Dizziness.
  • Feeling shaky (tremor).
  • Feeling jittery, irritability.
  • Mood swings.
  • Cold tremors, fever.
  • Loss of appetite, diarrhoea.
  • Changes in the taste of food (dysgeusia), dry mouth, toothache.
  • Difficulty concentrating.
  • Feeling of tiredness (fatigue) and sleepiness, drowsiness or lack of energy (lethargy).
  • Ringing in the ears (tinnitus).
  • Rapid or irregular heartbeat.

For a complete list of side effects, see the package leaflet. Consult a doctor if you experience any side effects.

What Mysimba contains

The active substances are:

  • Naltrexone hydrochloride and bupropion hydrochloride.
    Each tablet contains 8 milligrams of naltrexone hydrochloride, equivalent to 7.2 milligrams of naltrexone, and 90 milligrams of bupropion hydrochloride, equivalent to 78 milligrams of bupropion.

The other ingredients are:

  • Tablet core: microcrystalline cellulose, hydroxypropyl cellulose, lactose anhydrous, lactose
    monohydrate, cysteine hydrochloride, crospovidone, magnesium stearate, hypromellose, edetate disodium, colloidal silicon dioxide, and indigo carmine aluminium lake (E132).
  • Filmcoating: poly(vinyl alcohol), titanium dioxide (E171), macrogol (3350), talc and indigo carmine aluminium lake (E132).

The manufacturer of Mysimba is:

Central Pharma Contract Packaging Ltd.
Caxton Road, Bedford, Bedfordshire, MK41 0XZ
United Kingdom

Package leaflet

Read the package leaflet before use. You can download the official package leaflet of Mysimba here.

Patient Leaflet(s)
Medication information
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