The national medical regulator is warning people not to try and import ivermectin products, saying a number of them are fake and have smaller doses of active ingredients in them than advertised.
The Therapeutic Goods Administration (TGA) and other health authorities have already spoken out against people using the anti-parasitic medication to self-treat COVID-19.
Ivermectin is usually used to treat things like scabies, mites and worms.
The TGA is now also advising people not to buy ivermectin products online, after tests on a number of imports found they were counterfeit.
It found that, of the products tested, three had less than the active ingredient amount advertised on the label.
"Counterfeit products may contain undeclared and hazardous ingredients that could cause a serious adverse reaction," it said.
"They may also be contaminated because of a lack of manufacturing and testing standards."
The TGA said it would continue to work with Australian Border Force to target and stop counterfeit ivermectin products from entering Australia.
The regulator also took the opportunity to again tell people not to use the medication as a way to treat or prevent COVID.
"It is very dangerous to take large doses of ivermectin and there is insufficient evidence to validate its safe and effective use for COVID-19," it said.
The drug's manufacturer, Merck Sharp & Dohme (MSD), has also urged people not to use it to treat COVID-19.
"[There is] no scientific basis for a potential therapeutic effect against COVID-19 from pre-clinical studies," it said.
"[There is] no meaningful evidence for clinical activity or clinical efficacy in patients with COVID-19 disease, and a concerning lack of safety data in the majority of studies."
