There has been a large increase in the number of unauthorised weight loss products seized by Revenue, according to the Health Products Regulatory Authority.
In this month alone, 8,000 such products were seized, four times the quantity seized in all of last year, which was 2,000.
HPRA has noticed a significant rise in online ads making false claims about medicines, devices, and cosmetics.
Speaking on RTÉ's News at One, Director of Compliance with the HPRA Grainne Power said the surge in the number of products is believed to be linked to "quite elaborate ads that look completely believable, but making numerous false claims about the medicines they're promoting".
In particular, she said, "GLP-1 products that are presenting themselves as what are called 'micro-needle patches,' that they say contain the product."
"These ads are using the HPRA's logo to falsely endorse these products," she said.
GLP-1 products are primarily used as prescription medicines to treat diabetes and weight loss.
The products are often marketed online as ozempic-type weight loss medicines.
The active ingredient - semaglutide - is sold under the brand name Ozempic as an anti-diabetic medication used for the treatment of type 2 diabetes.
Ozempic is approved for use in Ireland as a diabetes drug, but has not been listed for reimbursement as a treatment for obesity under the Drug Payments Scheme.
Ozempic costs around €150 a month if you are taking it for weight-loss purposes and a rival product called Wegovy reportedly costs €220 a month.
Ms Power said there are a couple of "red flags" that people should be aware of: "The first one is that the HPRA will never endorse a specific medicine in that way; our logo would never be used on any medicine.
"And the second red flag is that it is not legal in Ireland to promote a prescription medicine to the general public at all."
She said these are "two clear signals" to people to avoid being tempted by products being promoted in these ads.
Ms Power said the consistent message remains that the only safe place to buy prescription medicines is from a pharmacy with a doctor's or prescriber's prescription.
The 'medicines' do not "represent authorised products at all", she added.
"They are products that don't exist, and particularly these GLP1 patches, they don't exist as an authorised medicine anywhere in the world, to the best of my knowledge."
She said the HPRA has "no idea" what is in the products and "no confidence" about their safety.
False medicine ads are being promoted through Facebook and also through fake social media profiles that can purport to "represent well-respected" healthcare professionals or institutions in Ireland, said Ms Power.
"When the ads pops up and you show an interest, you're then targeted, and if you click into it, what you are redirected to is an e-commerce platform outside the jurisdiction, and it is typically 'Shopify.'"
When the HPRA finds the ads, it contacts Facebook and Shopify and requests them to remove the ads and their links.
Companies have engaged with the HPRA and taken some of the material down, "but not all," and the authority continues to escalate its contact with "both of those organisations and continue to co-operate with them", said Ms Power.
She added that HPRA has engaged at European level with its "peer organisations" to raise the matter more generally, as it is not just an Irish issue, it affects patients "all over Europe".
