The drug, which was once associated with controversial head shops, was seized in Rathcoole in North-West Cork by members of the Kanturk District Drugs Unit.
Gardaí said the seizure was made as part of “a planned operation targeting the sale and supply of controlled drugs” after they stopped and searched a car at 11.30am on Tuesday.
They are still awaiting analysis of the drug which will be carried out at Garda headquarters in Dublin, but suspect it could be mephedrone with a street value of approximately €42,000.
The drug is a synthetic stimulant of the amphetamine and cathinone classes and is reportedly being manufactured in large quantities in China.
It comes in the form of tablets or a powder, which users can swallow, snort or inject. However, gardaí say it is possible that the drug could also be crystal meth.
Two men in their 50s were arrested at the scene and taken to Bandon Garda Station where they were detained under Section 2 of the Criminal Justice (Drug Trafficking) Act 1996.
While that legislation would have allowed gardaí to detain them for up to seven days, they were released from custody a number of hours later.
A Garda spokesman confirmed a file will now be prepared for the DPP.
He added that members of the Kanturk District Drugs Unit and the West Cork Divisional Drugs Unit were continuing their inquiries in relation to the distribution of synthetic drugs in the North Cork region.