Alcohol and drugs are substances that everyone recognizes as incompatible with driving. But someone who has swallowed an over-the-counter painkiller or anti-inflammatory with a sip of water before getting behind the wheel rarely worries that they might affect concentration, reaction time, and quality of vision.
The problem of drug interference with driving ability is quite complex and often underestimated. Many substances are potentially dangerous, even if it is not easy to establish the exact extent of the risk. In laboratory tests, groups of volunteers face different trials: driving regularity, difficult routes, reaction to obstacles. From the times obtained – and the errors made – the "weight" of the tested drug on psychophysical integrity is defined. However, the results are not perfectly transferable to a real traffic situation, where different factors can come into play, either positively (e.g., driving practice) or negatively (e.g., adverse weather).
The potentially most dangerous drugs are those that act on the central nervous system. This primarily includes anxiolytics, "tranquilizers," used to control anxiety and emotional disorders, but also as sedatives before exploratory clinical examinations. Obviously, they cause drowsiness and a reduction in psychomotor performance, risks that are often underestimated. It is often thought that only prolonged use is detrimental; in reality, even a single dose can significantly impair driving ability for several hours.
The same reasoning applies intuitively to antidepressant and antipsychotic drugs. In these cases, however, the pathology itself advises against driving, which the doctor may explicitly prohibit their patient from doing.
The consequences of taking antihistamines are rather well-known: drowsiness, mental confusion, dizziness. These drugs are used as antiallergics, but not only. They are also found in nasal decongestants, cough suppressants, and analgesics. It is better to prefer second-generation ones: the interactions with the nervous system are modest.
AIFA (Italian Medicines Agency) has launched a public consultation to draw up a list of drugs dangerous for driving; the list is available online, here
