Mounjaro, known as the “King Kong of weight loss drugs”, will be available to patients on the NHS, but this week it was announced the medication will be prioritised to people with the highest needs – with the rollout expected to extend over 12 years.
We take a look at why the medication is in such demand and the impact it could have on the nation’s health.
What is Mounjaro?
Mounjaro is one of a growing number of weight loss jabs and is produced by the pharmaceutical company Eli Lilly. It is a once-a-week injection that contains the drug tirzepatide and is also used to help improve blood sugar in people with type 2 diabetes.
How does it differ from Wegovy?
Wegovy is also licensed for weight loss, but contains the drug semaglutide and is made by the Danish company Novo Nordisk.
Both semaglutide and tirzepatide mimic a hormone produced in the body called GLP-1 – a substance that is released in the gut when we eat. This hormone slows the rate at which food is emptied from the s tomach, acts on the brain to reduce appetite and triggers an increase in the production of insulin.
However, tirzepatide also mimics another hormone known as GIP (glucose-dependent insulinotropic polypeptide).
This dual action appears to be why tirzepatide is associated with greater weight loss. One study, looking at data from two clinical trials of people with type 2 diabetes spanning at least 68 weeks, found tirzepatide resulted in a weight loss of 17.8% of participants’ body weight relative to placebo compared with 12.4% relative to placebo for semaglutide.
Who is eligible for Mounjaro?
Mounjaro has been approved by the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) for adult patients with a body mass index (BMI) of 30 or more, as well as those with a BMI of 27 or more who also have weight-related health problems such as high blood pressure or heart problems.
Patients can already buy the drug privately, although concerns have been raised over whether there is enough oversight of the sale of weight loss jabs though online pharmacies.
NHS England has also been given the green light to use the drug, although the National Institute for Health and Care Excellence (Nice) has recommended it be used only for people with a BMI of more than 35 and at least one weight-related illness, encompassing about 3.4 million people in England.
However, those hoping for an NHS prescription may have to wait: on Thursday it was announced NHS England would be introducing the medication over a 12-year period. Only about 220,000 people are expected to benefit during an initial three-year period, with patients receiving care from specialist weight management services prioritised.
The Nice guidance on tirzepatide will also be used in Wales to underpin their own plans for a rollout.
Why is introduction on the NHS so slow?
This appears to be down to the scale of demand, and fears the NHS – and in particular GPs – could be overwhelmed.
That is because of differences in the way the various jabs are accessed. While Wegovy can be prescribed only on the NHS through specialist weight management clinics, Mounjaro can be used in all settings, including primary care or specialist weight management services, although full details have yet to be confirmed.
Prof Jonathan Benger, the chief medical officer at Nice, said: “We have had to make this difficult decision in order to protect other vital NHS services and also to test ways of delivering this new generation of weight loss medications.”
He also said Nice wanted to help NHS England carefully manage the introduction of tirzepatide “to ensure that other services are not impacted in a disproportionate way”.
What are the public health implications?
According to the latest Health Survey for England, 64% of adults were overweight or obese in 2022, with recent estimates suggesting the situation is costing the NHS £19.2bn a year.
Benger said: “Tirzepatide and other drugs like it, such as semaglutide, will help people living with obesity to lose weight, and as a result will reduce their risk of developing heart disease or having a stroke.”
Ministers have also expressed hopes the jabs could help people back into work, with trials under way to explore whether tirzepatide can have a health economic impact.
Are there any concerns?
While many experts have welcomed the development of effective weight loss medications, they have cautioned that jabs such as Mounjaro and Wegovy do not tackle the root causes of obesity, stressing that policymakers must do more about the environment that has caused the health crisis.
They also said that for the greatest effects, such medications must be used alongside support on nutrition, physical activity and behaviour – something that could be problematic if tirzepatide is made available through primary care.
Dr Simon Cork, of Anglia Ruskin University, said GPs often did not feel qualified or able to provide this at the necessary level.
“The duration of time over which tirzepatide will be rolled out will be frustrating for many people who want urgent help with tackling their weight but is understandable given the resources available in the NHS,” said Cork. “If these drugs are going to be made available to all who need them, then increasing the workforce that provide the support to these patients to maximise their effectiveness is going to take time and potentially a large restructuring of how that support is currently delivered.”
