They’re often billed – irresponsibly, say doctors – as weight-loss “wonder-drugs” or “miracle” jabs. But amid hype about celebrity crazes and concerns about a counterfeit-riddled black market, healthcare professionals are keen that an important message is not lost: the class of medicines known as GLP-1 agonists, abbreviated to GLP-1s, can transform the health and life of people with obesity.

Although barriers remain, from stigma to affordability, it’s been a milestone year in Ireland for GLP-1s, with Mounjaro becoming available on prescription in the Republic in February and Wegovy following at the end of March.

Wegovy, made by Novo Nordisk, contains semaglutide, the same active ingredient found in the Danish company’s most famous drug, Ozempic, which has been used here for the treatment of type 2 diabetes since 2018. Ozempic remains the most common shorthand for GLP-1s.

The drugs work by mimicking a natural hormone (GLP-1) that’s released after eating, signalling satiety – feeling full – to the brain. This suppresses patients’ appetites and better regulates their blood sugar.

[ Weight-loss jabs and me: ‘My obesity is not a battle I win and walk away from. It’s something I live with’ ]

Mounjaro is made by US pharma giant Eli Lilly (also known as just Lilly) and, like Wegovy, it is a weekly, self-injectable medicine. Its active ingredient, tirzepatide, is a “dual agonist”, meaning it stimulates the receptors for two hormones in the body: GLP-1 and also GIP, which regulates appetite.

Further clinical breakthroughs are expected to lead to the arrival of new drugs