Motor Vehicle Accidents and Benzodiazepine
Previous studies have indicated an association between the use of tricyclic antidepressants and benzodiazepines and the occurrence of road-traffic accidents. This study evaluated 19,386 first time traffic accidents to assess the influence of prescribed psychoactive drugs. 1731 drivers had ingested either a dosage of antidepressant (793), benzodiazepine (916), selective serotonin-reuptake inhibitor (334), or other psychoactive drug (138) the day of the accident. The researchers then went ahead and compared risk factors within the four drug groups.
The authors found no increased risk in subjects who were taking tricyclic antidepressants, selective serotonin-reuptake inhibitors, or other psychoactive drugs. The authors did find, however, a statistically significant increase in risk for those using benzodiazepines. Of particular concern and interest to the authors was benzodiazepine's possible detrimental effect on driving. Benzodiazepines tend to impair reaction time and psychomotor function, as well as induce sedation. Chronic exposure to the drug, however, is thought to be safe. The authors explain:
"We found that users of anxiolytic benzodiazepines were at significantly increased risk of road traffic accidents and that this risk was dose-related. However, users of hypnotic benzodiazepine were not at increased risk, probably because the hypnotic benzodiazepine are taken at night and have little residual pharmacological effect the next day, whereas anxiolytic drugs are taken during the day then they would be expected to have greatest effects during driving. The one exception was the short-acting hypnotic zopiclone...this hypnotic has residual effects that impair car-driving performance, which might explain the association with accidents. "
The authors also found that the risk decreased with age, the highest risk affecting those under 30. They propose that perhaps younger people drive earlier, before they have developed a tolerance to the sedative. The authors conclude that users of "long-half-life anxiolytic benzodiazepines and zopiclone...should be advised not to drive."
Barbone F, McMahon A, Davey P, et al. Association of road-traffic accidents with benzodiazepine use. The Lancet 1998;352:1331-1336.
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