According to the experts, we vastly underestimate the serious effect prescribed drugs have on our driving ability, writes David Labanyi
A SENIOR pharmacology expert has warned that driving while under the influence of certain medicines can double the risk of a crash.
Speaking at a conference in Dublin on medicine and motoring yesterday, Prof Han de Gier said most people don't realise - or choose to ignore - the dangers of driving while taking medication and said the true level of crashes involving medicine is underestimated.
The professor of pharmaceutical care at the University of Groningen in the Netherlands said one reason for low awareness was poor-quality information on medicine packaging.
"I doubt the pharmaceutical firms do the right research to find the facts needed to improve the warnings. . . Normally, patients are not aware or not able to identify whether or not they are impaired. But at the same time they are at risk."
Prof de Gier began studying the relationship between medicines and driver impairment in 1975 and is involved in the European Driving under the Influence of Drugs, Alcohol and Medicines (Druid) project.
Druid has brought together experienced researchers and organisations from 18 European countries to study the impact of psychoactive drugs and other intoxicants on road safety. It will recommend regulations for allowable limits for driving under the influence of alcohol, drugs and medicines.
Speaking ahead of the conference, organised by the Pharmaceutical Society of Ireland (PSI), Prof de Gier said the likelihood of being in a crash doubled for drivers taking certain medicines, particularly benzodiazepines - a class of psychoactive drug often prescribed to treat anxiety, stress and panic attacks.
They can cause drowsiness and have been linked with a higher incidence of crashes in a series of studies.
"The chance of being involved in a crash is doubled on many of these drugs, which makes it similar to what you have with a blood alcohol level of 80mg - the legal alcohol limit in Ireland," Prof de Gier said.
He referred to a Canadian study of 5,931 drivers, 482 of whom were killed in a crash. Tests found that 3.6 per cent of the drivers surveyed were taking benzodiazepines and accounted for 8.5 per cent of those killed. The impact of these drugs is particularly significant during the first two weeks of treatment, he added.
Prof de Gier noted that, among patients taking two or more combinations of psychoactive medicines, the levels of impairment escalated. "People are generally not aware of this fact because their information is purely based on the sometimes illogical information on medicine packets," he said.
He said there is also little awareness of the potential dangers of driving after consuming alcohol while on certain medication. "Benzodiazepines are very famous for this. When you start using combinations with alcohol, the risk will increase synergistically. It becomes several times higher and the driver impairment will be beyond the level of the normal drug.
"We would like to improve the labelling system and that is why we are looking at a classification period. We want a tiered system that allows patients to see whether the drug produces a minor, moderate or severe level of impairment."
Prof de Gier says it is important to establish impartial risk thresholds for prescription drugs and illegal drugs and for this information to be given to pharmacists and doctors.
The Druid project has set a deadline of 2010 for the creation of these thresholds and a labelling system.
Prof de Gier believes the true scale of benzodiazepine involvement in fatal crashes is underestimated, as there is no mandatory testing of dead drivers for the presence of prescription drugs.
"One of the first steps is to start a routine check of all of the people killed in accidents to find out what is in their blood."
One large-scale study of drug driving in the Australian state of Victoria tested 436 drivers hospitalised after crashes and found that 60 had traces of benzodiazepines in their blood. Almost one-third of these were women aged 65 and over.
The PSI, the statutory regulator for pharmacists and pharmacies, published a public awareness leaflet, Medicines and Driving, at yesterday's conference.
PSI president Dr Bernard Leddy said certain prescription or non-prescription medicines may impair driving ability. Motorists "must be made aware that their medication may affect mental alertness, co-ordination and therefore driving skills", Dr Leddy said.
The Road Safety Authority (RSA) is concerned at the role of over-the-counter drugs and prescription medicines in road crashes. It had planned to run a drug-driving awareness campaign this year after making the issue a priority, but was forced to shelve this plan due to a 1.6 per cent budgetary cutback.
Last year, gardaí detected 218 cases of drug-driving on Irish roads.