The additive effects of alcohol and benzodiazepines on driving
September/October 2010
Abstract:
OBJECTIVES: To examine the relationship between the combination of alcohol and benzodiazepines and the risk of committing an unsafe driver action.
METHODS: We used data from the Fatality Analysis Reporting System (1993-2006) on drivers aged 20 or older who were tested for both alcohol and drugs. Using a case-control design, we compared drivers who had at least one unsafe driver action (UDA; e.g., weaving) recorded in relation to the crash (cases) to drivers who did not (controls).
RESULTS: Drivers who tested positive for intermediate- and long-acting benzodiazepines in combination with alcohol had significantly greater odds of a UDA compared to those under the influence of alcohol alone, up to blood alcohol concentrations (BACs) of 0.08 and 0.05 g/100 ml, respectively. The odds of a UDA with short-acting benzodiazepines combined with alcohol were no different than for alcohol alone.
CONCLUSIONS: This study demonstrates that the combination of alcohol and benzodiazepines can have detrimental effects on driving beyond those of alcohol alone. By describing these combined effects in terms of BAC equivalencies, this study also allows for the extrapolation of simple, concrete concepts that communicate risk to the average benzodiazepine user.
Discussion:
The results of this study allow the combined effects of alcohol and benzodiazepines to be expressed in terms of a BAC equivalency, or points at which the combination creates detriments equivalent to those for alcohol alone. For example, using 0.08 g/100 ml as a benchmark, the findings in this study suggest that this equivalence was reached with intermediate benzodiazepines in combination with a BAC of approximately 0.03 g/100 ml. Using 0.05 g/100 ml as a benchmark, this equivalence was reached with long benzodiazepines in combination with a BAC of only 0.02 g/100 ml; further, drivers under the effects of an intermediate half-life benzodiazepine were already beyond the detriments associated with a BAC of 0.05 before alcohol had been consumed. Short-life benzodiazepines combined with alcohol did not yield risks significantly different from those found with alcohol alone. This finding is in line with previous research which demonstrated that short half-life benzodiazepines do not affect driving ability.
This research also provided a better look at the type of person likely to drive under the combined influences of benzodiazepines and alcohol. Combination users were younger and more likely to be male than drivers in the benzodiazepine-only subgroups, and in fact were most similar to those in the alcohol-only group. Combination users also had slightly worse driving records than their benzodiazepine-only counterparts, suggesting that they may be greater risk-takers.
Finally, underlying medical conditions for which benzodiazepine may have been prescribed are unknown. Although research has suggested that anxious and insomniac patients do not differ from healthy controls when it comes to driving ability under the effects of benzodiazepines, the possibility of these conditions confounding the results cannot be ruled out...
September/October 2010
Abstract:
OBJECTIVES: To examine the relationship between the combination of alcohol and benzodiazepines and the risk of committing an unsafe driver action.
METHODS: We used data from the Fatality Analysis Reporting System (1993-2006) on drivers aged 20 or older who were tested for both alcohol and drugs. Using a case-control design, we compared drivers who had at least one unsafe driver action (UDA; e.g., weaving) recorded in relation to the crash (cases) to drivers who did not (controls).
RESULTS: Drivers who tested positive for intermediate- and long-acting benzodiazepines in combination with alcohol had significantly greater odds of a UDA compared to those under the influence of alcohol alone, up to blood alcohol concentrations (BACs) of 0.08 and 0.05 g/100 ml, respectively. The odds of a UDA with short-acting benzodiazepines combined with alcohol were no different than for alcohol alone.
CONCLUSIONS: This study demonstrates that the combination of alcohol and benzodiazepines can have detrimental effects on driving beyond those of alcohol alone. By describing these combined effects in terms of BAC equivalencies, this study also allows for the extrapolation of simple, concrete concepts that communicate risk to the average benzodiazepine user.
Discussion:
The results of this study allow the combined effects of alcohol and benzodiazepines to be expressed in terms of a BAC equivalency, or points at which the combination creates detriments equivalent to those for alcohol alone. For example, using 0.08 g/100 ml as a benchmark, the findings in this study suggest that this equivalence was reached with intermediate benzodiazepines in combination with a BAC of approximately 0.03 g/100 ml. Using 0.05 g/100 ml as a benchmark, this equivalence was reached with long benzodiazepines in combination with a BAC of only 0.02 g/100 ml; further, drivers under the effects of an intermediate half-life benzodiazepine were already beyond the detriments associated with a BAC of 0.05 before alcohol had been consumed. Short-life benzodiazepines combined with alcohol did not yield risks significantly different from those found with alcohol alone. This finding is in line with previous research which demonstrated that short half-life benzodiazepines do not affect driving ability.
This research also provided a better look at the type of person likely to drive under the combined influences of benzodiazepines and alcohol. Combination users were younger and more likely to be male than drivers in the benzodiazepine-only subgroups, and in fact were most similar to those in the alcohol-only group. Combination users also had slightly worse driving records than their benzodiazepine-only counterparts, suggesting that they may be greater risk-takers.
Finally, underlying medical conditions for which benzodiazepine may have been prescribed are unknown. Although research has suggested that anxious and insomniac patients do not differ from healthy controls when it comes to driving ability under the effects of benzodiazepines, the possibility of these conditions confounding the results cannot be ruled out...
