Active ingredients of Mysimba Naltrexone and Bupropion

Mysimba – a new combinatorial treatment of obesity and overweight

Obesity is a major health concern in the western world, and in Europe alone, every fifth adult is in medical terms considered to be obese with a BMI (Body Mass Index) of 30 or more – a three-fold increase over the last two decades. Of course, this is a major issue for society in general with increasing healthcare costs, but not the least for the affected person who is more likely to suffer from severe conditions such as diabetes, heart attacks, and strokes. In this article, we will discuss the use of Mysimba, a new treatment of obese and overweight patients.

We are aware of the dangers of obesity, and although we understand the simple connection between overweight and too much food intake and too little exercise, we don’t always understand the more complicated systems in our bodies that regulate apatite and hunger. Unfortunately, this often leads to a misunderstanding and prejudices towards patients with obesity. For many, it seems simple to eat less and do more exercise, but the causes of obesity and the situation of the obese patient is simply not that simple.

Fortunately, scientists at Orexigen Therapeutics were dedicated to, in detail, understand why obese patients eat more, and what happens in the brain when we are feeling hungry, and based on their knowledge they have developed Mysimba a new combinatorial treatment for obesity consisting of two active compounds: naltrexone and bupropion.

Feeling hungry when you are not supposed to

Eating is a natural thing to do when we feel hungry, and it is very difficult to tell someone to eat less when they are hungry. That is why Mysimba potentially could be helpful for patients who want to lose weight. The combination of naltrexone and bupropion, in Mysimba, affects the center in the brain that works with signals that regulate your appetite and regulates when you feel like eating and not.

From when we are children our brains learn to register and interpret signals from the body to form a functional and healthy eating pattern, and unfortunately, in obese patients, this is not always working properly. In fact, obese and overweight patients will often feel hungry even though they had enough food to eat, and the brain fails to interpret the information that is provided by the obese person’s body. Mysimba, containing naltrexone and bupropion, address this issue and help the brain to appreciate when the body had enough food.

In theory, Mysimba fine-tunes appetite and promote weight loss

To understand how naltrexone and bupropion in Mysimba restore the ability to properly interpret hunger signals from the body we need to know how the brain works at a cellular level. The brain is build up by a cell type called neurons, and between neighboring neuronal cells, there are constant signals being transmitted and received. Mysimba acts to fine-tune some of these signals.

Bupropion, the first active substance in Mysimba, stimulates the release of endorphins and alpha-Melanocyte-stimulating hormone (α-MSH) by the neurons in a specific area of the hypothalamus in the brain. The neurons in this area form what is called the mesolimbic system, which is a dopaminergic reward system, and when endorphins and α-MSH are released by the neurons in this area of the brain they produce an effect of you feeling satisfied and full instead of hungry.

Naltrexone, the second active substance in Mysimba, potentiate the effect of bupropion, by inhibiting so-called feedback mechanisms in the mesolimbic system that eventually kicks in to reduce the levels of hormones that are being released by bupropion. Together naltrexone and bupropion create a potent and prolonged effect of you feeling full, thus adjusting your apatite back to normal. Not feeling hungry anymore by the naltrexone and bupropion treatment the patient eats less food and loses weight.


So do Mysimba and the additive effect of naltrexone to bupropion work in practice?

The additive effect of naltrexone in Mysimba has been confirmed in a number clinical studies where the effect seen on weight loss was more pronounced with the combination of naltrexone and bupropion compared to with bupropion alone.

The main evaluation of Mysimba, and the combination of naltrexone and bupropion, on weight reduction, is based on the results of four double blinded, placebo controlled, studies (NB-301, NB-302, NB-303, and NB-304), that together include a number of 4 536 patients. Three of the studies (NB-301, NB-302, and NB-304) evaluated the effect after 56 weeks of treatment, and the fourth (NB-303) after 28 weeks of treatment.

In all studies, doctors included instructions to the patients in regards to calorie intake and physical activity in combination with the Mysimba treatment, and in study NB-302 a behavior modification program consisting of 28 counseling meeting in groups was added in addition to help patients lose more weight.

Remarkably 85% of the patients on Mysimba treatment in had a weight reduction of 5% or more compared to control groups, and perhaps even more interesting the biggest weight loss was found in the study where patients also received counseling, with an 8% or more weight loss in patients on Mysimba. These studies confirm that a combination of naltrexone and bupropion has a positive effect on weight loss.


Human complexity requires a complex solution to weight loss

The combined effect of Naltrexone and bupropion in Mysimba manage to help overweight patients to eat less and lose weight, through the act of bupropion that increases signals letting the brain that your body full and naltrexone that prolong and induce this effect. This can be seen as a complementary treatment to the patient’s own effort to change eating habits and do more exercise. Indeed, studies done on naltrexone and bupropion treatment suggest that a more holistic approach to weight loss, where Mysimba is one integral part, is suitable to give the maximum effect.

Humans are complex, and seldom are there easy explanations to why people have medical problems, and the development of Mysimba is, therefore, a good example of how understanding and increased knowledge about the complexity of a medical problem generates new types of therapies. In different medical fields more and more attention is in fact given to the combinatorial use of active components to make new type drugs.


– Beware, Mysimba is not suitable as a drug for certain patients group, and before considering Mysimba, or any drug, as treatment you should always consult with your doctor.