What is Mysimba - naltrexone, bupropion used for?
Mysimba is an indicated medicine, in addition to diet and physical activity, to promote weight management in adult patients:
- obese (with a body mass index - BMI - 30 or more);
- overweight (BMI between 27 and 30) and weight-related complications such as diabetes, abnormally high levels of fat in the blood or high blood pressure.
The BMI is a parameter that provides information on body weight in relation to height. Mysimba contains the active ingredients naltrexone and bupropion, which are individually authorized in the EU for other uses.
How is Mysimba - naltrexone, bupropion used?
Mysimba is available as prolonged-release tablets containing naltrexone 7.2 mg and bupropion 78 mg and can only be obtained with a prescription. The expression "prolonged release" means that naltrexone and bupropion are released from the tablet slowly, over a few hours.
Treatment with Mysimba begins with taking a single tablet in the morning. The dose is gradually increased over 4 weeks to reach the recommended dose of two tablets twice a day, preferably taken with food. The response to treatment and the tolerability of the medicine must be monitored periodically; in patients who develop certain side effects, such as an increase in blood pressure, treatment must be stopped. Treatment with Mysimba must also be stopped if patients have not lost at least 5% of their initial body weight after 4 months of therapy. For more information, see the package leaflet.
How does Mysimba - naltrexone, bupropion work?
The exact mechanism of action of Mysimba is not entirely known, but the two active ingredients, naltrexone and bupropion, act on the brain areas that regulate food intake and energy balance, as well as reducing the activity of the centers that control the sensation of pleasure associated with food consumption. The action of the two active ingredients administered simultaneously causes a reduction in appetite and the amount of food consumed by patients and increases their energy expenditure, helping them to adhere to a low-calorie diet and to lose weight.
What benefit has Mysimba - naltrexone, bupropion shown during the studies?
The effects of Mysimba in reducing body weight have been demonstrated in 4 main studies involving around 4, 500 obese or overweight patients, during which Mysimba was compared with a placebo (a dummy treatment). Participants in the studies took the medicine as part of a weight control program, which included a cycle of sessions and counseling on diet and physical activity. The main measures of effectiveness were the percentage reduction in body weight over 28 or 56 weeks of treatment and the number of patients who registered a weight loss of at least 5%. The studies also took into account the number of patients who achieved a greater weight loss of at least 10%, and the results were analyzed using various methods, in order to take into account the number of patients who did not complete the studies (about 50% over the course of a year). In three of these studies the average weight loss of patients treated with Mysimba was between 3.7 and 5.7% compared with 1.3-1.9% seen with placebo. The percentage of patients treated with Mysimba who lost at least 5% of the initial weight was between 28 and 42% compared to 12-14% of patients treated with placebo. About 13-22% of subjects treated with Mysimba lost at least 10% of their initial weight compared to 5-6% of subjects treated with placebo. In the other study, which included a more intense session, the overall weight loss was greater during the study: 8.1% with Mysimba and 4.9% with placebo. Approximately 46% and 30% of patients treated with Mysimba achieved a weight reduction of 5% and 10%, respectively, compared with 34% and 17%, respectively, of placebo-treated subjects. The extent of improvement with Mysimba compared to placebo was similar with the use of different analysis methods, although more modest benefits were observed with more conservative methods (which excluded any signs of improvement in patients who did not complete the study). Treatment efficacy was more pronounced in subjects who completed 56 weeks of treatment or who lost at least 5% of their original body weight over 4 months.
What is the risk associated with Mysimba - naltrexone, bupropion?
The most common side effects of Mysimba (which may affect more than 1 in 10 people) are nausea, vomiting and constipation; equally common (observed up to 1 in 10 people) are dizziness and dry mouth. For the full list of all side effects reported with Mysimba, see the package leaflet. Mysimba should not be used in certain individuals at high risk of side effects, including patients with severe impairment of renal or hepatic function, subjects with uncontrolled arterial hypertension, subjects who have had seizures or suffering from psychological disorders or those with brain tumor, or individuals who have recently stopped taking alcohol or certain drugs. For the full list of limitations, see the package leaflet.
Why has Mysimba - naltrexone, bupropion been approved?
The Agency's Committee for Medicinal Products for Human Use (CHMP) is of the opinion that the effectiveness of the medicine in promoting weight loss, while being limited, is sufficient to be considered clinically significant and that the obligation to re-evaluate the treatment after a 4-month cycle it should by itself ensure that the medicine continues to be used only in those subjects where adequate benefit is observed. As for safety, although it has concerns about possible cardiovascular effects (cardiovascular outcomes) and a slightly increased risk of convulsions, the CHMP considers the most common side effects to be largely manageable, as patients can stop therapy in the event that become annoying. The intermediate results of an ongoing study on cardiovascular outcomes were analyzed during an evaluation; despite this, the CHMP also recommended constant monitoring of the cardiovascular effects of the medicine. In light of the available evidence, the CHMP decided that Mysimba's benefits are greater than its risks and recommended that it be approved for use in the EU.
What measures are being taken to ensure the safe and effective use of Mysimba - naltrexone, bupropion?
A risk management plan has been developed to ensure that Mysimba is used as safely as possible. Based on this plan, safety information has been included in the summary of product characteristics and the package leaflet for Mysimba, including the appropriate precautions to be followed by healthcare professionals and patients. Furthermore, the company that markets Mysimba will prepare an information pack for the doctors who prescribe the medicine, including a guidance document on the interruption of treatment in subjects who do not respond to therapy or in the presence of fears for side effects. The company will also carry out a further study to evaluate the effect of the medicine on the heart and blood vessels. Further information is available in the summary of the risk management plan.
Other information about Mysimba - naltrexone, bupropion
On 26 March 2015, the European Commission issued a marketing authorization for Mysimba, valid throughout the European Union. For the full version of the EPAR and the summary of the Mysimba risk management plan, consult the Agency's website: ema.Europa.eu/Find medicine / Human medicines / European public assessment reports. For more information about treatment with Mysimba, read the package leaflet (also part of the EPAR) or contact your doctor or pharmacist. Last update of this summary: 03-2015
