A new drug to treat Type 2 Diabetes has been approved by Australia’s Therapeutic Goods Administration and is now available in Australian pharmacies. Australia now joins the US, the EU and Canada in offering Mounjaro as a treatment to diabetics.
Mounjaro is the brand name of the drug Tirzepatide. It’s similar to the popular drugs Semaglutide (sold under the name of Ozempic) and Dulaglutide (sold as Trulicity) in a few ways – it’s an injectable medication contained in a pre-filled syringe pen, it works by affecting hormone receptors in the gut, and it regulates blood sugar levels as well as assisting weight loss.
However, it differs from Ozempic and Trulicity in one important way. While Ozempic and Trulicity mimic the effect of one hormone, Mounjaro mimics two.
Pep talk
When you eat, your intestines detect the rise in blood sugar and spurt out two specialised hormones: GLP-1 (glucagon-like peptide 1) and GIP (glucose-dependent insulinotropic peptide). These hormones tell the pancreas to make more insulin and less glucagon in preparation for the sweet times ahead.
Insulin works to lower your blood sugar by helping your cells absorb the extra glucose from food. Glucagon does almost the opposite, asking the liver to excrete stored glucose in between meals. This complicated system of messengers usually works to keep blood sugar levels steady throughout the day.
As well as counseling the pancreas, GLP-1 also stops by the stomach for a chat about its work performance. A speedy stomach processes food faster, but results in feeling hungrier sooner. A slower stomach stays fuller for longer, but can feel heavy and uncomfortable. GLP-1 asks the stomach to slow down as it digests.
All this secretion and messaging happens very fast – in around two minutes. But Mounjaro, Ozempic and Trulicity, although they mimic GLP-1, degrade slower and last much longer. This means the medications only need to be taken once a week.
Hitting the sweet spot
For hormones to work, they need to be properly received by the organ they’re trying to talk to. Organs like the pancreas have special receptors like locks that only specific hormones can fit into. Ozempic and Trulicity are shaped like GLP-1 to fit into the receptors that recognise GLP-1. But Mounjaro is shaped more like GIP, so it fits into GIP receptors as well as being able to fit into GLP-1 receptors. This means it effectively mimics two hormones at the same time.
Research suggests this makes Mounjaro even more effective than the other drugs in regulating blood sugar and assisting in weight loss.
One study showed that even small doses of Mounjaro worked better than Ozempic, while another reported that it was superior to insulin glargine (Lantus) at controlling blood glucose levels.
However, the studies also noted that Mounjaro had a greater severity of side effects compared to the other treatments.
Side effects
Every medication has side effects, and since Mounjaro works on intestinal hormones, it’s not surprising that it has a number of digestive ramifications.
In the studies above, low doses of Mounjaro had about the same rate of nausea, diarrhoea and vomiting as 1mg of Ozempic, at 18%, 12% and 8% of trial participants respectively. On the highest dose of Mounjaro, 22% of patients experienced nausea, 16% experienced diarrhoea, and 10% experienced vomiting. Other common side effects include decreased appetite, constipation, indigestion and abdominal pain.
However, there’s one side effect that looks set to make Mounjaro as popular as Ozempic has already been: easy weight loss.
Size effects
Many people living with Type 2 Diabetes are categorised as overweight or obese. Higher weight, especially around the middle of the body, can lead to fat accumulating in the liver and pancreas. This in turn affects their function, resulting in less insulin being produced, and then working less effectively. Research shows that losing weight alone can help manage diabetes and even lead to a remission of the disease.
Like other new diabetes medications, Mounjaro has been approved to treat Type 2 Diabetes as a standalone treatment in the case that patients can’t take Metformin, or in combination with other diabetes treatments, including diet and exercise. But like Ozempic, it’s likely that Mounjaro will be widely prescribed “off-label” for its weight loss effects.
Ozempic’s weight loss effects are, by now, well-known. Its popularity has led to high prices and widespread unavailability. As Mounjaro has been shown to be slightly more effective than Ozempic in assisting weight loss – with patients losing 15 – 20% of their body weight on Mounjaro compared to 15% for Ozempic – its introduction into the market may help address the severe shortage.
Supply effects
If the drug itself isn’t enough to make patients nauseous, its cost might. Having been knocked back for listing on the Pharmaceutical Benefits Scheme due to its high price, Mounjaro is only available as a private, unsubsidised prescription. This means it’s likely to cost hundreds of dollars per dose. While it might be tempting to turn to the internet for a dubiously-sourced bargain, doctors warn patients not to seek Mounjaro and similar drugs online.
Mounjaro also has to be stored in the fridge and administered weekly, which, along with its cost, makes it difficult for disadvantaged populations to benefit from it. As people living on lower incomes aren’t easily able to maintain healthy lifestyles and have a higher rate of obesity, this issue of access means that those who would benefit the most from this class of drugs are the least able to afford it.
Mounjaro began to be distributed to pharmacies in mid October. The TGA has given Mounjaro its Black Triangle Scheme warning, which will mean Mounjaro will be subject to additional monitoring in Australia.
