Almost every conversation about weight loss medicine now starts with the GLP-1 family — Wegovy, Mounjaro and, since this month, Foundayo. Mysimba is the one that isn’t. It works on a completely different part of the system, which is exactly why it has a place: it’s the option for people who can’t take a GLP-1 medicine, didn’t tolerate one, or want a tablet that targets cravings rather than fullness.
Mysimba combines two established medicines in one prolonged-release tablet: naltrexone (8 mg), used for decades in addiction medicine, and bupropion (90 mg), an antidepressant also licensed to help people stop smoking. Together they act on the brain’s reward and appetite centres — the hypothalamus and the mesolimbic pathway — reducing hunger and, more noticeably for many people, the pull of cravings and comfort eating.
The dose is built up over four weeks to keep side effects tolerable: one tablet in the morning for week one, one morning and one evening in week two, two in the morning and one in the evening in week three, then the full dose of two tablets twice a day from week four. Tablets are swallowed whole with food and must not be crushed or split. A pack of 112 lasts four weeks at the full dose, and we supply four weeks at a time with a pharmacist check-in at each collection.
Mysimba is less powerful than the GLP-1 medicines: trials show an average of around 5–9% body-weight loss over a year, compared with 15–20% for the injections. The guidance is clear about checking it’s working — if you haven’t lost at least 5% of your starting weight after 16 weeks, it should be stopped. The commonest side effects are nausea, constipation, headache, dizziness, dry mouth and trouble sleeping, most of which ease as the dose settles.
People with a BMI of 30 or more (or 27 or more with a weight-related condition such as type 2 diabetes or high blood pressure) who either can’t use a GLP-1 medicine or prefer not to. It’s also worth considering if your eating is driven more by cravings and emotional triggers than by physical hunger, because that’s the pathway it targets.
This is where Mysimba needs more care than the GLP-1 tablets. It is not suitable for anyone with uncontrolled high blood pressure, a history of seizures or epilepsy, a current or past eating disorder (bulimia or anorexia), bipolar disorder, or anyone using opioids or in opioid withdrawal. It can’t be combined with MAOI antidepressants, and it interacts with a number of other medicines. It isn’t used in pregnancy, breastfeeding, severe liver or kidney disease, or over the age of 75. Our pharmacist checks every one of those, and your blood pressure, before supplying it.
Use the suitability check on our weight loss clinic page. It works out your BMI, asks a few screening questions and books a free phone consultation. If Mysimba is the right fit, we’ll get you in for a short in-person consultation and blood pressure check, then you collect from your nearest branch.
Pharmacist-led weight loss clinic at all six Sandwell Pharmacy Group branches. Injections or tablets — we’ll tell you which we’d actually recommend for you.
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