The European Medicines Agency (EMA) published new advice in July 2024 concerning the combined use of opioid medications and the weight loss drug Mysimba (naltrexone/bupropion). The advice warns that naltrexone, one of the active substances in Mysimba, can prevent opioid effectiveness. Therefore, it advises patients taking Mysimba to inform their doctor they are taking it well in advance of any surgery, as they should stop taking it two days prior to taking any opioid medication.
Mysimba has been available to patients on private prescription in the UK since 2017 and in Europe since 2015, but has never been available on the NHS as a result of NICE’s decision not to recommend it, due its lack of cost-effectiveness. There have been several regulatory updates since which indicate this decision is unlikely to change; for example, in 2019 the MHRA warned that the medication could cause dizziness and somnolence (sleepiness), which could impair driving.
The new EMA advice includes a recommendation that opioid-dependent patients should receive opioids agonists such as methadone, and that those going through acute opioid withdrawal should not be prescribed Mysimba at all.
MySimba is an alternative to NICE-recommended weight loss medications like Semaglutide (though there is currently a shortage of these) and Liraglutide, both GLP-1 receptor agonists, as well as Orlistat, a pancreatic lipase inhibitor. Patients affected by the new MySimba advice can ask their GP about these alternatives.
Further Reading:
- European Medicines Agency ’EMA advises about risks of using weight loss medicine Mysimba with opioids’.
