The Health Products Regulatory Authority has reported a 40% increase in the number of illegal prescription medicines detained by its enforcement section last year.
It said that 948,915 tablets were seized, compared with 673,906 the previous year.
The main products seized by authorities were anabolic steroids (47%), sedatives (23%) and erectile dysfunction medicines (13%).
It amounted to 449,411 anabolic steroids and 222,470 sedative products.
The HPRA says the supply of these medicines into Ireland is illegal and consumers can have no guarantees about the safety or quality of prescription medicines they are seeking to buy outside of the regulated pharmacy setting.
Last year, the authority saw a big increase in the volume of anabolic steroids being detained but a decrease in the number of sedative products.
HPRA Director of Compliance John Lynch said that the abuse and misuse of anabolic steroids can have serious consequences for the long-term health of individuals who take them, including liver damage, blood clots, heart attacks and strokes.
There were 3,866 individual enforcement cases and six court prosecutions initiated by the HPRA last year.
The number of abortifacient medicines seized last year was lower than in the previous year.
There were 487 abortion pills seized last year, compared with 536 the previous year.
Of the abortifacient tablets detained last year, 49 contained Misoprostol and 38 contained Mifepristone.