Australia's medicines regulator has issued a warning about counterfeit peptide products after a patient tore their oesophagus following severe vomiting from a product sold as retatrutide. The person required hospital treatment.

Retatrutide is an experimental weight loss peptide that has not been approved by the Therapeutic Goods Administration or by regulators overseas, and it cannot legally be prescribed or sold in Australia. Peptides are chains of amino acids that act as chemical messengers in the body, involved in hormone activity, digestion, immune defense and tissue growth, and the peptides in retatrutide mimic hunger hormones.

What was actually in the vial

The TGA obtained a sample of the product the patient had taken and found no retatrutide in it at all. What it did contain was semaglutide, a different hunger-targeting peptide, at a concentration roughly eight times higher than levels found in approved semaglutide products the agency has assessed.

That number is the whole story. A user believing they were taking one unapproved drug was in fact taking a large multiple of a second one, with no label to tell them otherwise.

Sold under initials

Despite having no approval anywhere, the drug has been widely promoted on social media and offered on hidden markets under names including retatrutide, Reta, R-10 and R-20. It often arrives in unmarked vials.

The naming convention is worth noting on its own. Products marketed by an initial and a number are not products with a quality record attached.

What the regulator said

TGA chief medical adviser Prof Robyn Langham said the biggest risks with unapproved peptide products are not knowing what is in the vial, how much of it, whether it is sterile, or whether it contains contaminants or toxins. She said those risks are particularly concerning for injectable products, where non-sterile manufacturing can raise the risk of infection and harmful immune responses including anaphylaxis.

Langham added that people who self-inject face further risks including incorrect dosing, unsafe technique and serious adverse reactions.

Not the first warning

Victoria's health department issued a similar alert in June after being notified of six cases of acute liver toxicity associated with products labeled as retatrutide. TGA head Prof Anthony Lawler said imported and illegal products are not subject to the same controls over quality or efficacy as approved medicines.

Bottom line

Australia's chief medical officer has previously warned publicly about unapproved and non-prescribed peptides following reports of liver damage, inflammation and severe allergic reactions. The unresolved question is enforcement: the supply channel here is social media and hidden markets, and a regulator's warning reaches a different audience than the one buying unmarked vials.