Driving under the influence of khat--alkaloid concentrations and observations in forensic cases.

The use of the herbal stimulant khat (Catha edulis FORSK) is maintained by immigrants from countries where it is part of their cultural life (Arabian Peninsula and eastern Africa). In western countries the drug and its effects are largely unknown and no experience in evaluating impairment symptoms due to the khat-alkaloids, e.g. cathinone, cathine and norephedrine exists. Blood and urine samples from khat users involved in 19 cases of suspected driving under the influence of drugs were analysed and correlated with the results of medical examination and police officer reports. In 3 cases impaired driving and in 10 cases marked impairment of psychophysical functions was observed such as effects on the nervous system (slow pupil reaction to light, dry mouth, increased heart-rate), trembling, restlessness/nervousness, daze/apathy/dullness, impairment of attention, walking and standing on one leg. However, the alkaloid concentrations assayed in blood did not correlate with the impairment symptoms. Apart from an acute phase of indirect sympathomimetic action the development of habituation and withdrawal symptoms must also be considered in explaining the diversity of effects observed. From these results it can be concluded that chewing khat may severely impair driving ability, but may also be without noticeable effects.