In July, the Pharmaceutical Benefits Advisory Committee (PBAC) ruled that a new and highly-effective type 2 diabetes drug should not be added to Australia’s Pharmaceutical Benefits Scheme (PBS).

The drug’s brand name is Mounjaro, its active ingredient is tirzepatide –and it’s a second-generation competitor to celebrity favourite Ozempic.

In late September, Mounjaro – which is reportedly more effective at weight loss and control of blood sugar than Ozempic – was released in Australia anyway.

Participants experienced a mean weight loss of 21 per cent over 72 weeks in a clinical trial for obesity management.

The King Kong of weight loss

The Seven Network described Mounjaro as “the King Kong of weight-loss medication”, and reported it would cost Australians up to $320 a month at the least without a subsidy.

Other reports say a higher-dose prescription would cost $600 a month.

Seven noted that because Mounjaro was being issued as a private prescription, the cost would be determined by pharmacists.

Within weeks, despite the lack of a subsidy, stocks of Mounjaro – a tweaked version of which was formally approved as a weight-loss drug by the US FDA in November – had run out.

The Therapeutic Goods Administration advised that “availability of all strengths of Mounjaro (tirzepatide) will be limited until 31 August 2024 due to unexpected high demand”.

According to the Sydney Morning Herald, the PBAC acknowledged that some methods of taking Mounjaro “were superior for short-term weight loss when compared to semaglutide – the active ingredient in Ozempic, which is on the PBS for diabetes – but not in all circumstances”.

The committee said “Mounjaro did not meet its requisite cost-effectiveness test, and that the company would need to lower its price significantly for Mounjaro to be considered again”.

Diabetics being left in the lurch

Stocks of Ozempic – with the active ingredient semaglutide – have been critically short since May 2022. And there is some pressure to provide alternatives.

According to a newsGP report, the TGA in September played the heavy by advising that “prescribers should not initiate semaglutide prescriptions without a compelling clinical reason, while alternative medications should be considered for patients who are already taking the drug”.

Bottom line: Pharmacists were shocked at how quickly stocks of Mounjaro ran out. The drug was meant to help diabetics who have been left in the lurch because of the run on Ozempic stocks, an issue blamed on social media.

For some of the Ozempic’s history and madness see here, here, and here. And here is what it has done for Oprah Winfrey.

So what is the new drug?

Semaglutide (Ozempic) is one of a new class of drugs that acts as a glucagon-like peptide-1 (GLP-1) receptor agonist.

In short, this helps slow down digestion and reduces appetite.

Tirzepatide (Mounjaro) does something new. It contains two hormones instead of one.

The glucagon-like peptide-1 (GLP-1) receptor agonist works in tandem with a glucose-dependent insulinotropic polypeptide (GIP) receptor agonist.

Together, they have been found so far to help “regulate the body’s blood sugar levels, slow down digestion and reduce appetite, which makes a person feel more full and eat less, leading to weight loss”.

Semaglutide v Tirzepatide

Semaglutide is self-administered by an EpiPen into belly fat.

Tirzepatide is self-administered with a needle and vial. Users need to be trained up.

According to Healthline, a 2023 study found that tirzepatide resulted in greater weight loss than semaglutide.

Although it costs more, “researchers concluded that tirzepatide is more effective and better value”.

A 2021 study also found that tirzepatide was more effective at weight loss. However, these studies looked at people with type 2 diabetes, and obesity alone.

Tirzepatide has also been found to be more effective at controlling blood-sugar levels in people with uncontrolled diabetes. That’s a terrific finding.

A new study found that tirzepatide “significantly lowered the systolic blood pressure of nearly 500 adults who had obesity and took the medication for 36 weeks, or about eight months, in a subset of an international clinical trial”.

This too is a great finding: Bringing blood pressure under control is one of the challenges of treating type 2 diabetes.

The new research was published this week in Hypertension, an American Heart Association journal.

Side-effects of each medication

The side-effects of tirzepatide and semaglutide are similar, probably  because they work in a similar manner.

Moderate side-effects of tirzepatide and semaglutide can include:

• Constipation or diarrhea
• Upset stomach, nausea, and vomiting
• Headaches
• Abdominal pain
• Fatigue
• Low blood sugar (hypoglycemia).

More severe side-effects of tirzepatide and semaglutide may include:

• Vision changes
• Pancreatitis
• Kidney failure
• Gallbladder issues
• Allergic reactions.

Both these medications have boxed warnings for the risk of thyroid C-cell tumours.

A boxed warning is the most serious warning from the FDA.

There are also questions about the side-effects of tirzepatide in people without type 2 diabetes.

There may be more limitations and side-effects that are still unknown based on current research, and how new these types of medications are for use in weight loss.

Mounjaro is made by US pharmaceutical company Eli Lilly.

Ozempic is made by Novo Nordisk, Denmark.

Other weight loss drugs of a similar class, but even more effective, are under development and can be expected to sell out quickly when they come on the market.