Establish limits for fitness to drive with prolonged use of ICADTS class III medication

The Dutch assessment of driving ability with the use of potentially dangerous
drugs when driving refers to the classification of the International Council on
Alcohol, Drugs and Traffic Safety (ICADTS). Medications are categorized in
class I (safe to drive) , class II (be careful when driving) and class III (do
not driving).
This classification is mainly based on double-blind research in healthy
subjects using the medication only once, or just briefly. There is, however,
insufficient knowledge of everyday effects in chronic users of these drugs.
The Netherlands has a large number of chronic users of ICADTS class III drugs.
It is very likely that the majority of these ambulatory patients also drives
the car.
Being able to determine when a patient is fit to drive despite the use of class
III drugs has major social and economic benefits, both for the user which then
is fully mobile, and because he is better employable on the job market.
The proposed study provides general standards and limits concerning use of
chronic medications and fitness to drive, and can thus form the basis for
science-based regulation of antidepressants, sleeping pills and tranquilizers.

The aim is to determine on the basis of the results of this study whether there
is measurable effect on the ability to drive after long term use of ICADTS
class III drugs. To achieve this goal drugs will be tested out of the groups
most commonly used, namely hypnotics (sleeping pills), anxiolytics and
antidepressants in therapeutic doses. The neuropsychological assessment of
fitness to drive focuses on the following cognitive domains: attention and
processing speed, reaction time/ psychomotor functions, sensory - perceptual
function, executive function and alertness/vigilance.

In each of the three medication groups (hypnotics, anxiolytics and
anti-depressants) 40 subjects will be included (= 120 patients in total + an
expected maximum of 5% dropouts who will be replaced). In each medication group
the 40 patients will be matched with 40 healthy control subjects (= 120 cotrol
subjects in total + an expected maximum of 5% dropouts who will be replaced).
Matching will be done on: age, gender en driving experience. Furthermore, an
additional group of 20 patients will be enrolled, they all have to use 2 or
more ICADTS category III medicines (= Multi User Group). Condition is that also
in this extra group all used ICADTS Category III drugs have to be part of the 3
studied medicine groups. The matching of the 20 patients participating in the
multi-user group will take place by attempting to link them to a control
subject, which has already been linked to a patient in one of the drug groups.
If there is no good match available in this group, a new control subject will
be sought and tested.
In each medication group 2 periods of medication consumption will be
distinguished namely longer than 6 months but shorter than 3 years and more
than 3 years (at steady dosages). Every effort shall be made to achieve an
equal division of the patients between the 2 consumption groups.
When necessary a division of at least 15 and a maximum of 25 is permitted. In
the group of 20 patients taking more than one drug from the ICADTS category III
this distinction will not be made.

In this study chronic users of ICADTS class III medication will be included.
The drugs tested will be those from the most common used medication groups,
namely hypnotiscs, anxiolytics and anti-depressants in therapeutic doses.

Prior to participation patients and control subjects who are interested in
participating in the study fill in a medical questionnaire. This is presented
to the Medical Supervisor and he assess whether the person is eligible to
participate in the study. Each volunteer comes to the test center twice. The
first time is for a training session. During this visit a short screening
(height, weight , vision) will be executed, the volunteer fills in some
questionnaires and the cognitive tests are all explained and practiced.
Thereafter, the test day takes place. Both visits will last approximately 5
hours.
In this study, chronic users of ICADTS class III drugs are included. We
therefore expect no side effects of these drugs during their participation.
While driving in the simulator, it is possible that subjects experience
simulator sickness (similar to motion sickness). This is explained in advance
and they will be closely monitored while driving. It is made clear that they
can stop the investigation at any time.