Australians are buying an unapproved weight-loss drug from suppliers whose websites list the product as “for research use only” or “not for human consumption,” but sell by the milligram and ship it to residential addresses.
Retatrutide has been hailed the king of peptides by fitness influencers, and its pharmaceutical maker hopes it’ll be the new Mounjaro, but there is a very good reason the drug can’t be legally sold anywhere in the world: its safety and effectiveness are still being tested, and people injecting potentially dangerous knock-offs are risking serious side effects.
“This is a serious problem,” said Dr Ian Musgrave, a molecular pharmacologist and toxicologist at the University of Adelaide. “Retatrutide is still experimental. We don’t know the length and frequency of side effects … that the problems with the stuff people are buying online are multifold.”
Pharmaceutical company Eli Lilly (maker of Mounjaro) is running phase 3 clinical trials of the synthetic peptide, which has not been approved by any regulator globally.
But on TikTok, Australian fitness influencers tout the benefits of “ret” with how-to guides, dosage recommendations and injecting advice, despite it being unlawful to advertise unregistered therapeutic goods.
Local distributors court customers in the comments, and users post unboxing videos of their vials of retatrutide powder arriving at their residential addresses.
“But it says on the disclaimer ‘not for human consumption’,” one TikTok user commented in response to a link for a website selling retatrutide and other peptides.
“[W]ho do you think they’re selling to? People that [sic] have laboratories in their house or something?”
A Lilly spokeswoman said: “No one can legally sell it for human use.”
“Counterfeit and black-market products are untested, unregulated and potentially dangerous — in some cases, deadly,” the spokeswoman said in a statement. “These products are not purified to pharmaceutical-grade levels and often come from illicit, unregulated foreign suppliers.”
A pharmacist in Sydney’s south recalled a customer who wanted to buy bacteriostatic water – sterile water used to reconstitute medicines – to inject his retatrutide.
Another customer asked to purchase 500 insulin syringes, which have a needle length ideal for injecting substances subcutaneously (under the skin) – the type used to inject peptides, just as retatrutide.
Its appeal extends beyond the peptides trend in the fitness and bodybuilding industries largely due to the mainstream popularity of GLP1 agonist weight loss drugs like Ozempic.
The synthetic peptide is a “triple hormone receptor”, engineered not only to activate the body’s GLP1 receptors but also two other receptors (glucose-dependent insulinotropic polypeptide and glucagon) involved in controlling insulin secretion, glucose uptake and energy expenditure, as well as decreasing gastric emptying and appetite.
“You’ve got this triple whammy,” Musgrave said. “I’ve seen some papers saying it’s gamechanger for controlling type 2 diabetes and as a potential weight loss drug.
“But like all drugs, it can have potential side effects,” he said. “It is entirely possible retatrutide will have the same side effects as other GLP1s, which are rare but serious. For example, the stomach can stop emptying completely, pancreatitis, or bowel obstructions.”
There have also been reports of study participants losing too much weight too fast, “which can cause potentially dangerous complications and has to be carefully monitored”, Musgrave said.
The retatrutide people are buying online, with no assurances of its purity, poses even greater risks, he said.
“It’s a string of amino acids and folds up in a very particular three-dimensional shape – like a key for the lock of the receptor. But if you’re not careful, it may fold up incorrectly.
“It may form clumps, which, when you inject it, can lead to highly undesirable immune responses, [such as] anaphylactic reactions,” he said.
Some suppliers may be selling “genuine research articles”, Musgrave said, “but that’s for squirting on cells or putting them into enzyme preparations, which is not the same as being sterile and sufficiently pure for human use.”
The US Food and Drug Administration warned that companies have been illegally selling retatrutide falsely labelled “for research purposes” or “not for human consumption” directly to consumers for human use with dosing instructions.
TikTok has banned searches for “retatrutide”, and removes content that it finds violates its guidelines, but the testimonials and instructional videos still flourish.
The Therapeutic Goods Administration said it had requested the removal of more than 13,700 unlawful advertisements from digital platforms in the 2024-2025 financial year. The regulator did not indicate how many were for retatrutide or peptides.
“Retatrutide would not be high on the list of illegal substances customs [authorities] are looking for,” Musgrave said, “and the problem is nobody is really looking at this in any detail”.
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