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Prescription drug use and driving impairment warnings examined

By Nicole MacKee
Drivers taking prescription drugs may not have received warnings about potential impairment associated with the medication, US researchers have reported.

In an analysis of data from the 2013 to 2014 US National Roadside Survey, 7405 drivers reported taking a prescription medicine, with 78.2% reporting that the drug had been prescribed for their use.

Writing in the Journal of Studies on Alcohol and Drugs, the researchers said that 85.8% of those who had been prescribed sedatives and 85.1% of those who had been prescribed narcotics had received a warning from their health practitioner about potential driving impairment associated with these drugs. However, only 57.7% of drivers who had been prescribed stimulant medication and 62.6% of those taking antidepressant medications said they had been warned about possible driving impairment.

Professor Olaf Drummer, Professor of Forensic Medical Science in the Department of Forensic Medicine at Monash University, said the provision of warnings was likely to be similar in Australia with both the prescribing doctor and the pharmacist having an obligation to warn patients if a prescription drug may impair driving.

‘Not all drivers who are on these drugs will necessarily have adverse effects that might affect their driving skills, but they would normally be given appropriate warnings and it’s up to the driver to decide whether they are impaired and should not drive. Sedation, a side effect with many of these drugs, often dissipates with repeated use as tolerance sets in.’

Professor Drummer was the lead author of a 2016 study of fatally injured drivers in Victoria that found that drivers taking medicinal drugs alone were unlikely to show a significant crash risk, even if the drugs were potentially impairing (Forensic Sci Int 2016; 265: 17-21). The researchers examined coroners’ files and toxicology records of 2638 fatally-injured drivers and found that drivers taking opioids or antidepressants (mostly serotonin reuptake inhibitors) were not at a significantly increased crash risk compared with those in the control group, while there was a suggestion of an increased crash risk for taking benzodiazepines.

‘Benzodiazepines will cause impairment if they are misused, but there wasn’t much evidence for individual drivers misusing [these drugs] based on blood concentrations alone,’ he said, adding that the Victorian findings were in line with global study results.

‘For the most part, modern drugs that treat depression and opioids don’t have a major risk in terms of causing crashes, as compared to alcohol and illicit drugs, particularly cannabis and ice – they are the two main drugs we are concerned about in Australia.’
J Stud Alcohol Drugs 2017; 78: 805-813.

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