Carlow Roads Policing Unit stopped a vehicle on the Pollerton Road in Carlow on Thursday night.
An oral specimen from the driver "proved positive for cocaine".
The driver was arrested and a blood specimen was taken at the station. Gardaí await the results from the Medical Bureau of Road Safety.
Cocaine is a controlled drug under Misuse of Drugs Act, and is illegal to possess.
Gardaí said: "Never drive whilst under influence of an intoxicant."