The relationship between blood benzodiazepine concentration and vehicle crash culpability

Abstract

OBJECTIVE: The purpose of this study was to determine the relationship between blood benzodiazepine concentration and crash risk. METHODS: Blood samples from 2500 injured drivers were analyzed for benzodiazepines and the relationship between concentration and crash risk was assessed using culpability analysis. Benzodiazepine concentrations were expressed as a proportion of the peak concentration of the drug in blood or plasma for a standard therapeutic dose of the drug. RESULTS: There were 68 drivers (2.7%) who tested positive for at least one benzodiazepine. Of these, 16 (23.5%) also tested positive for alcohol. Drivers who tested positive for benzodiazepines, either alone or in combination with alcohol, had a higher culpability rate than drug-free drivers. There was a significant linear relationship between benzodiazepine concentration and culpability for drivers who tested positive for benzodiazepines alone. CONCLUSION: The results here provide clear evidence of increased culpability associated with benzodiazepine use, which was marked at higher concentrations.