Patient suffers torn oesophagus after using unapproved peptide falsely labelled as retatrutide

A patient who used an unapproved peptide labelled as the weight-loss drug retatrutide has suffered a potentially fatal torn oesophagus.

The medicines regulator, the Therapeutic Goods Administration (TGA), has revealed details of the case to the ABC as part of its latest warning against the use of unapproved peptides.

It said the peptide user experienced uncontrollable vomiting and required hospitalisation.

The TGA said laboratory testing found the product contained no retatrutide, but instead had undeclared semaglutide, the drug used in weight-loss drugs Ozempic and Wegovy.

The testing also revealed an exceptionally high dose of the drug.

"The amount of semaglutide detected was approximately eight times higher than the level found in semaglutide products assessed by the TGA," the regulator's safety advisory said.

The results follow testing by the ABC in partnership with the University of Queensland, which found vials of black market retatrutide had much higher doses than declared on their labels.

Melbourne gastroenterologist Darcy Holt has treated patients who have suffered adverse effects from injecting unapproved counterfeit retatrutide.

He said a torn oesophagus, which is the tube that carries food and liquid to a person's stomach, was a medical emergency.

"A tear of the oesophagus can mean that stomach contents can enter the part of the body where the heart and main blood vessels are, and infection and inflammation in that area are extremely serious.

"Many of the peptides we are talking about do have gastrointestinal effects and require titration of dose to minimise those effects.

"But in overdose, the gastrointestinal effects can be severe. A high dose of the drug can cause extreme nausea and forceful vomiting leading to an oesophageal tear."

Dr Holt said patients had also suffered liver toxicity and severe secretary diarrhoea from taking unapproved peptides, which can also be life-threatening.

A new TGA safety advisory said retatrutide was currently undergoing clinical trials in humans and has not been approved by it or any comparable international regulator.

It should not be used outside of a clinical trial setting, the note said.

The TGA's chief medical advisor, Robyn Langham, said "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 its sterile or whether it contains other contaminants or toxins".

"These risks are particularly concerning for injectable products, where contaminated or non-sterile manufacturing can increase the risk of infection and harmful immune responses including anaphylaxis," she said.

Dr Holt said he had seen a noticeable increase in patients telling him they were using unapproved retatrutide this year.

"Over the past three to six months the use of peptides like retatrutide has gone from something that basically we would never elicit from a patient's medication list to something that now quite frequently pops up when we're asking someone what drugs they're taking," he said.