The Irish Medicines Board, Customs and gardaí have seized over 51,600 counterfeit and illegal medicines in a week long operation.
The tablets, capsules and creams were seized as part of a campaign targeting the online sale of medicines.
The value of the haul is estimated at over €150,000.
The initiative was part of an international week of action co-ordinated by Interpol and involving over 80 countries.
In Ireland, 492 packages were detained by customs. Most of the substances were for weight loss, erectile dysfunction or were mood stabilisers.
Other substances found were steroids, antibiotics, painkillers, cardiac medicines, cholesterol lowering products, cancer medicines and insulin.
Many of the products have either too little or too much active ingredient, have no active ingredient at all or contain banned substances.
IMB Chief Executive Pat O' Mahony said under Irish law the sale of prescription-only medicines by mail order is prohibited. This includes the internet supply of prescription medicines.
In the last four years, 470 websites have been closed in Ireland.
As part of the same operation over 150 packages of counterfeit and illegal medicines were seized in Northern Ireland.
