There were almost 700 cases of people driving under the influence of both cocaine and cannabis last year.
A 13-year-old and a 95-year-old were among those who were arrested for drink or drug-driving in 2021.
The Medical Bureau of Road Safety received just under 5,900 blood and urine samples for alcohol and/or drug testing last year, after drivers were tested by Gardaí.
Alcohol was the most frequently detected, and the median level of alcohol in drivers' blood was around three-times the legal limit for most motorists.
Driver arrested 15-times
One driver was over eight-times above the legal limit.
Another driver was arrested 15-times in the space of three months for drink-driving.
The bureau said alcohol remains a very significant danger on Irish roads.
Figures show that of 4,300 samples tested for drugs last year, over 3,400 were found positive for at least one substance.
Of those, 36% detected at least two drugs - with cannabis and cocaine the most common combination.
Other than alcohol, the three most commonly detected substance was cannabis, followed by cocaine and benzodiazepines.
Over 140 drivers had all three of these drugs in their system while behind the wheel last year.
The youngest arrested person for drink or drug-driving last year was 13, and the oldest was 95.
However 82% were under the age of 45.
Sinn Féin's transport spokesman Darren O'Rourke said new laws are needed to clamp down on those who drive with several drugs in their system.
"New legislation is needed and Government needs to legislate to tackle polydrug use," he said.
"There is a commitment in the current Road Safety Strategy that this would be done, and it needs to happen without delay to tackle the increasing problem of polydrug use."