Mysimba is a medication used in conjunction with exercise and diet to help with weight loss and the management of obesity in adults. It is commonly used for people who are considered to be obese: i.e. who have a BMI (body mass index) of 30 or more. Mysimba contains two main active ingredients: naltrexone hydrochloride and bupropion hydrochloride which work on the brain to reduce cravings and hunger. Mysimba is only suitable for adults over 18 years of age and must be taken as prescribed by a doctor. Mysimba UK is approved by the European Health Commission.

What is Mysimba?

Mysimba is a slow-release medicine that assists with weight loss in conjunction with a calorie-controlled diet and a regular exercise program. Mysimba contains the two main ingredients naltrexone and bupropion which work on the brain to reduce the desire to eat. When we eat the brain induces a feeling of reward and positive stimuli. So when we overeat the brain continues to give us that feeling of reward, which is one reason why some people eat too much and find it difficult to manage their food intake.

Naltrexone is formally known as a mu-opioid antagonist and bupropion is a norepinephrine and dopamine reuptake inhibitor. Naltrexone affects the cravings to eat that we sometimes get even if we are not hungry. Bupropion is an appetite suppressant which means it stops you from feeling hungry and so you eat less.

Note that bupropion is also an ingredient contained in some anti-depressants and so it is not advisable to take Mysimba in conjunction with anti-depressant medication. Overeating (particularly of foods with high sugar and fat content) combined with a lack of exercise can cause obesity.


Mysimba is usually prescribed for people who are obese (dangerously overweight with a body mass index of 30 or more). Body mass index (BMI) depends on the individual and is calculated based on a person’s weight, height and age.

Obesity is a dangerous medical condition that can affect your health. It can increase the risk of some health conditions such as:

  • Type 2 diabetes;
  • Heart problems;
  • High blood pressure;
  • Certain types of cancer;
  • Arthritis.

Obesity and weight gain can be caused by several factors including:

  • Overeating (particularly foods with high sugar and fat content);
  • Stress and anxiety;
  • Depression;
  • Some medications;
  • Genetic history;
  • A sedentary lifestyle (with the convenience of modern living we move less, walk less and do less exercise).

According to the World Health Organization, in 2016, 39% of women and 39% of men aged 18 and over were overweight worldwide.

Mysimba can assist with the management of weight gain and obesity if a person is not able to lose weight just with diet and exercise. Some people don´t burn calories as fast as others and this combined with poor eating habits and a lack of exercise can cause obesity, which can be dangerous for a person’s health.

When is Mysimba used?

Mysimba is used when a doctor believes a person needs medical intervention to help manage their weight. Mysimba is not available without a prescription. It should be used in conjunction with a suitable diet that is low in calories and alongside a regular exercise program. How do you use Mysimba?

When you first take Mysimba you build up the dose gradually, so your body becomes accustomed to it. After four weeks you should have reached the regular balanced dose that your doctor has prescribed. They will also discuss with you (usually after sixteen weeks) how long you should take Mysimba for. If you are advised to take Mysimba by your doctor for more than sixteen weeks this should be reviewed annually.

The manufacturer of Mysimba suggests that a person should lose 5% of their overall body weight after sixteen weeks of taking this medicine. They also recommend treatment is discontinued if this is not the case. Mysimba before and after reviews may help you decide if Mysimba is the right choice for you.

Mysimba comes in tablet form in 8mg/90mg individual doses. Each tablet contains 8 mg of naltrexone hydrochloride, which is the equivalent of 7.2 mg of naltrexone, and 90 mg of bupropion hydrochloride, which is the equivalent of 78 mg of bupropion. The tablets should be swallowed whole with water without chewing. The tablets should not be taken in conjunction with meals that have a high-fat content as there is the possibility the combination could cause an epileptic fit. Mysimba should only be taken by adults over 18 years of age.

What dosages are there?

When starting Mysimba the common first dose is one tablet once a day in the morning. Your doctor will advise you on the dose you should take, which is usually:

  • 1st week: one Mysimba tablet once a day in the morning;
  • 2nd week: one Mysimba tablet twice a day, one in the morning and one in the evening 3rd week: three Mysimba tablets each day, two in the morning and one in the evening;
  • 4th week and beyond: two Mysimba tablets twice a day, two in the morning and two in the evening The maximum recommended dose per day of Mysimba is two tablets to be taken twice a day.

What are the side effects of Mysimba?

The most common side effects that may occur when taking Mysimba are:

  • Insomnia;
  • Restlessness;
  • Anxiety;
  • Headache;
  • Disturbance in concentration;
  • Dizziness;
  • Hot flushes;
  • Palpitations;
  • Constipation;
  • Nausea;
  • Muscular pain;
  • Dry mouth.

If you experience any of these side effects you should tell your doctor.

When shouldn’t you use Mysimba?

Children should not take Mysimba, it is only suitable for adults over 18.

You should not take Mysimba if you are taking any of the following medicines:

  • Monoamine oxidase inhibitors: medicines used to treat depression or Parkinson’s disease such as phenelzine, selegiline, or rasagiline;
  • Opiates or medicines containing opiates: includes some medicines used to treat coughs and colds (for example, those containing codeine or dextromethorphan), medicines to control opiate addiction (such as methadone), pain medicines containing opiates (for example, codeine or morphine).

This is because naltrexone blocks the effects of opiates; if you take higher doses of opiates to overcome these effects of naltrexone, you may suffer from an acute opiate intoxication which could be life-threatening. Before taking Mysimba always check the ingredients of any medication that you are taking in addition to informing your doctor. The ingredients in some medicines used to treat depression can combine with the ingredients of Mysimba and may result in suicidal behaviour. You must tell your doctor if you are taking any medication for depression.

Even if not taking medication, anyone with a tendency towards depression should be closely monitored by their doctor when taking Mysimba. It is not advisable to drink alcohol while taking Mysimba as the combination can increase the risk of having a fit and cause psychological disorders.

If you have liver or kidney problems or if you are over 65 your doctor will consider whether Mysimba is suitable for you. Mysimba is not recommended for people over 75 years of age. Mysimba should not be used if you are pregnant, trying to become pregnant or breastfeeding. If Mysimba causes dizziness do not drive or operate machinery.

Does Mysimba interact with other medication?

As with all medicines, there is a possibility that Mysimba can interact with other medication.

When used in conjunction with naltrexone or bupropion some medicines may increase the risk of fits such as:

  • Anti-depressant medicines (for example, desipramine, venlafaxine, imipramine, citalopram and paroxetine) or medicines used for other mental health problems (for example, risperidone, thioridazine and haloperidol);
  • Steroids (except drops, creams, or lotions for eye and skin conditions or inhalers for breathing disorders such as asthma);
  • Quinolones (infection-treating antibiotics such as ciprofloxacin);
  • Theophylline (used for asthma);
  • Antihistamines (for hayfever, itching, and other allergic reactions);
  • Tramadol (a painkiller that is part of the opiates group);
  • Medicines to lower blood sugar levels (for example, insulin);
  • Medicines used to treat epilepsy (for example, valproate, carbamazepine, phenytoin and phenobarbital);
  • Malaria prevention medicines;
  • Sleep-inducing medicines (sedatives such as diazepam);
  • Medicines for Parkinson’s disease (for example, levodopa, amantadine or orphenadrine);
  • High blood pressure medicines (alpha or beta-blockers such as clonidine and metoprolol);
  • Medicines used to treat irregular heart rhythm (such as propafenone and flecainide);
  • Medicines used for the treatment of cancer (such as cyclophosphamide, tamoxifen and ifosfamide);
  • Medicines used for the treatment of strokes or heart disease (such as ticlopidine or clopidogrel);
  • Medicines used for the treatment of AIDS and HIV infection, for example, ritonavir and efavirenz.

If you are taking any of the above-listed medicines you should inform your doctor before you start taking Mysimba. It may be necessary to discontinue treatment of a particular medication and to have a blood test before commencing with Mysimba. A blood test will check there is none of the previous medication left in your system that could interact with the Mysimba.

However, you should not discontinue any medication without talking to your doctor first.

Note that it is also important to inform your doctor of any herbal medicines you may be taking.

Where can you buy Mysimba?

Mysimba can only be bought from a pharmacy if you have a prescription. You cannot buy it over-the-counter. Mysimba price is the standard cost of a UK prescription. You can buy Mysimba online following a consultation with a doctor if you are given a prescription.

Can I get Mysimba without a prescription?

No. Mysimba is a prescription-only medication.


MysimbaTM Approved in Europe for the Treatment of Obesity (n.d.). Retrieved April 27, 2019 from

PACKAGE LEAFLET: INFORMATION FOR THE PATIENT M Simba ® 8 m g/90 mg prolonged-release tablets (n.d.). Retrieved April 27, 2019 from uk.pdf-1510756511.pdf?_ga=2.221619352.1442913771.1601361456-2071352208.1599043266

World Health Organization. Global Health Observatory (GHO) data (n.d.) Retrieved April 27, 2019 from

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