Use of opioid medicines with Mysimba may lead to serious side effects.

After re-examining its initial opinion, EMA recommends updating the advice aimed at minimising the risks of interaction between the weight loss medicine Mysimba (naltrexone/bupropion) and opioid-containing medicines (including painkillers such as morphine and codeine, other opioids used during surgery and certain medicines for cough, cold or diarrhoea).

Opioid medicines may not work effectively in patients taking Mysimba, because one of the active substances in Mysimba, naltrexone, blocks the effects of opioids. There is also a risk of rare but serious and potentially life-threatening reactions, such as seizures and serotonin syndrome (a potentially life-threatening condition that results from having too much serotonin in the body), in people taking Mysimba together with medicines for treating depression and opioids.

To minimise these risks, patients and healthcare professionals are reminded that Mysimba must not be used in people who are dependent on opioids, people receiving treatment with opioid agonists such as methadone or buprenorphine and people going through acute opioid withdrawal.

People using Mysimba will be given a patient card to be carried with them at all times. The card will remind them to inform their doctor, in case of surgery, that they are using Mysimba. This is because Mysimba should be stopped for a minimum of three days before starting treatment with opioids, which are often used to prevent pain and discomfort during surgery and medical procedures.

The product information for Mysimba is being updated to reflect these changes.