What is the effect of drugs and medicines on driving behaviour?

Drugs and medicines affect fitness to drive differently for each type of drug, and there are also different effects within drug types [2] [3] [4]. Drugs have a numbing, stimulating or mind-changing effect on the brain, or a combination of these effects, which impair traffic task performance. Narcotics or sedatives such as cannabis and benzodiazepines (relaxing medicines) slow down the central nervous system activity, which, in traffic, may result in fatigue, diminished concentration, reaction time and information processing [2] [3] [4]. By contrast, stimulating drugs like amphetamines, cocaine and ecstasy accelerate the central nervous system activity, which may result in distraction, restlessness, aggressive and dangerous driving, increased risk taking and overrating one’s fitness to drive. Psychedelic drugs like LSD distort the perception of reality (hallucinogenic effect). Medicines with side-effects such as blurred vision, serious dizzy spells or sleep attacks may also affect fitness to drive [5]. The Dutch Association of Pharmacists (KNMP) has classified impairing medicines into three categories on the basis of the (acute) effect when starting the medication [6]. Recent years have shown a surge in the use of narcotics like GHB [7], ketamine [8] and laughing gas (nitrous oxide) [9] for recreational purposes.

Table 1 summarises the effects of the main drug and medicine groups on skills and functions relevant to safe driving or riding.

Medicine groups are too plentiful to mention them all in Table 1. The Dutch website www.rijveiligmetmedicijnen.nl/medicijnen/adviezen presents a comprehensive survey of information on medicines and fitness to drive.