Keaton T. Cameron-Burr
University of Massachusetts Medical School
Driving requires high level psychomotor abilities including accurate visual perception, sustained attention, and the ability to react rapidly to environmental stimuli.1 Opioid drugs may produce psychomotor impairment in both medical contexts and when consumed recreationally. However, patients on stable opioid regimens for chronic pain are usually considered to have developed tolerance to the impairing effects of opioids and may be considered “safe to drive” assuming appropriate medication adherence. Better understanding the effects of opioid drugs on individuals’ ability to operate a motor vehicle is imperative given the increased rates of use and abuse.2 While opioid drugs may increase the risk of an individual being involved in a motor vehicle accident, crash risk may also be highly dependent on confounding variables including but not limited to: the social context of opioid drug consumption, co-prescription of other drugs which may impair psychomotor function, and male gender.
Risk of crash involvement has been shown to be increased in users of prescribed opioid drugs in the first seven days after the date of dispensing across sexes, as well as in the first 4 weeks of treatment with opioids and acetaminophen/opioid combinations3,4. Severity of injury in road accidents involving opioid use may follow a loose dose-response relationship, with drivers being prescribed low doses of opioids shown to have 21% increased odds of road trauma, those prescribed moderate doses, 29% increased odds, and those prescribed high doses, 42% increased odds5.The use of prescription opioids by drivers has been found to be associated with significantly increased risks of crash involvement as well as crash culpability in multiple studies exemplified by Chihuri and Li in which authors found a >100% increased risk of crash involvement and >50% increased risk of crash culpability in groups taking prescription opioids6.
The story is, however, not so simple. In one study considering the relationship between crash culpability and opioid and/or benzodiazepine drug use, weakly positive associations of opiates and benzodiazepines with culpability were found, however, drivers showing the highest culpability rates were in the under 25 and over 65 age groups7. Further, in a study of the concentrations of morphine and codeine in blood of individuals arrested for driving under the influence in Sweden, 85% of opiate-positive DUID blood samples were from heroin users, rather than individuals using prescription opioids, indicating that DUID risk may more likely be associated with heroin use rather than prescription opioid use8. Finally, a massive study considering >8 million person-years examined whether a driver who recently filled a prescription for codeine or tramadol are at increased crash-risk involving serious injury to themselves or others. Of 83 codeine exposed subjects, 65 had been prescribed other psychomotor impairing drugs at or close to the time of filling their codeine prescription. As such, the authors failed to demonstrate that codeine use alone increases accident risk9. Similarly, in an analysis of drivers killed in road-traffic crashes in Sweden between 2003 and 2007, opioids were the second most commonly discovered class of drugs, interestingly, 83% of individuals involved in fatal crashes in this population were men and the concentration of substances in blood samples were found to be in the therapeutic range, indicating standard medical use as opposed to drug abuse10. Finally, both pain and pain treatment have been associated with traffic accident involvement11.
More work is needed to tease out the complex relationships between variables influencing safe motor vehicle operation, of which psychomotor function appears to be one of many. The data demonstrate that the ability to drive safely may be dependent on such confounding variables as male gender, what type of opioid drug is being consumed, and the context of consumption.