Fresh warning after patient suffers torn oesophagus from counterfeit drug sold as retatrutide

A consumer has suffered a torn oesophagus after uncontrollable vomiting linked to a counterfeit peptide sold as the experimental weight-loss drug retatrutide, prompting an urgent warning from Australia’s medicines regulator.

The person required hospital treatment after using the unapproved product, which was supplied in an unmarked vial, the Therapeutic Goods Administration (TGA) said on Tuesday.

Testing found the product contained no retatrutide but undeclared semaglutide at about eight times the level found in semaglutide products assessed by the TGA and included in the Australian Register of Therapeutic Goods (ARTG).

The case has sparked fresh concerns over the growing use of unapproved peptides in Australia, with products increasingly promoted online for weight loss, muscle growth and other health claims.

Retatrutide is currently undergoing clinical trials in humans and has not been approved by the TGA or any comparable international regulator.

Retatrutide is being developed by US pharmaceutical giant Eli Lilly as a potential next-generation weight-loss drug.

It belongs to the same family of medicines as Ozempic, Wegovy and Mounjaro, which have become household names for weight loss and diabetes treatment.

Ozempic and Wegovy contain semaglutide and activate the GLP-1 hormone pathway, while Mounjaro contains tirzepatide and activates GLP-1 and GIP.

Retatrutide activates three hormone pathways — GLP-1, GIP and glucagon — involved in appetite, blood sugar and metabolism.

The TGA said any product sold as retatrutide outside a clinical trial could be counterfeit.

Consumers have been urged to avoid unapproved peptide products, particularly those bought online or overseas or supplied in unmarked vials.

Eli Lilly said anything sold as retatrutide outside its clinical trials was illegal and its safety, purity and dosing could not be verified. “Taking unregulated substances poses serious health risks,” the company said.

TGA chief medical adviser Professor Robyn Langham said consumers faced the danger of not knowing what they were injecting.

“The biggest risks with unapproved peptide products are not knowing what is in the vial, how much of or even what substance it contains, whether it is sterile, or whether it contains other contaminants or toxins,” she said.