Letterkenny Roads Policing Unit stopped a driver outside Newtowncunningham for speeding as they had been detected travelling well in excess of the speed limit.
The driver then failed the roadside oral fluid preliminary drug test and tested positive for cannabis and cocaine.
The incident happened on Tuesday night.
Gardai have confirmed an arrest was made and the driver was charged to appear in court.
A Garda spokesperson said “Too many lives are lost on the roads because of excess speed and drink/drug driving.
“Too many lives are irreversibly turned upside down and too many families are devastated as a result of poor decisions when it comes to road safety.
“Please make the wise decision today to make road safety one of your top priorities.”
