A third driver has tested positive for drugs since new laws come into effect.
Gardai say the latest arrest happened on the Chapelizod Road when a male driver tested positive for cannabis.
On Saturday another male motorist – who was already banned from driving - was arrested after testing positive for cocaine on the N4.
Road safety campaigners have previously stated that young men are the main focus of this drug driving campaign.
The new laws came into force last Thursday.
Meanwhile, gardai say 185 people were arrested for driving under the influence over the Easter Bank holiday weekend.
That's compared to 125 arrests for the same weekend in 2016.