Prescription Drugs and Increased Traffic Accident Risk

Drivers taking certain types of prescription medications, including sedatives, tranquilizers, narcotic pain medications, antipsychotic drugs or antidepressants, are more likely to be involved in traffic accidents, according to a recent study.

These findings are an important reminder that patients prescribed certain medications should take appropriate precautions before driving vehicles or, in the case of some drugs, avoid driving altogether.

The study, published Nov. 16, 2010, in the online medical journal PLoS Medicine, was conducted in France, where medical experts classify all prescription medications into one of four levels based on the risk for driving impairment. Drugs classified as level 0 have no or negligible risk of driving impairment, whereas drugs assigned to levels 1, 2 and 3 have increasing risk of driving impairment, with level 3 drugs having major risk.

In France, for all drugs assigned to levels 1, 2 or 3, the following level-specific warning labels alerting patients to the risk of driving impairment are required to be printed on the outer packaging of the drugs:

• Level 1: “Be careful — Read carefully the patient leaflet before driving.”
• Level 2: “Be very careful — Take advice from a physician or a pharmacist before driving.”
• Level 3: “Danger: do not drive — Seek medical advice before driving again.”

In their PLoS Medicine study, Dr. Ludivine Orriols and his colleagues reviewed French police reports and a national police database, and identified all vehicle crashes between July 2005 and May 2008 that resulted in someone being injured. For each driver of a vehicle involved in a particular crash, they recorded the culpability of the driver and the national health care number (national ID) in the police report, if available. They then used the national ID of the drivers to match with data from the French national health care insurance database, and recorded the prescription drugs dispensed to each driver prior to the accidents.

The French researchers’ analysis included a total of 72,685 drivers involved in vehicle crashes. They compared prescription drug use by the 34,896 who were responsible for the accidents with the 37,789 who were not responsible. The percentages of the 72,685 drivers who were prescribed a level 1, 2 or 3 medication prior to the accidents were 10.2, 11.4 and 2.7, respectively.

The vehicles involved in these accidents included light vehicles (presumably cars, 58.9 percent), motorcycles (14.4 percent), motor scooters (13.9 percent), bicycles (5.3 percent), commercial vehicles (3.5 percent), heavy goods vehicles (1.9 percent) and other types of vehicles (2.2 percent).

Dr. Orriols and his colleagues found that the risk of being responsible for an accident resulting in an injury increased 1.24- to 1.40-fold for drivers who used at least one level 2 or level 3 medication. The proportions of all traffic accidents attributed to the use of either a level 2 or a level 3 medication were 3 percent and 0.7 percent, respectively. This higher proportion due to level 2 drugs is probably related to their more frequent use than the more dangerous level 3 medications.

Not surprisingly, the researchers also found that the risk of being responsible for an accident increased as the number of level 2 or 3 medications prescribed to a driver increased. For example, a driver using only one level 2 or 3 medication had a 1.06- to 1.22-fold increased risk of being responsible for an injurious crash, whereas a driver using more than three such medications had a 1.58- to 2.25-fold increased risk.

The classes of level 2 medications most strongly associated with an increased risk of a driver being responsible for an injurious vehicle accident included anti-seizure drugs, some antipsychotics, anxiolytics (tranquilizers, predominantly benzodiazepines) and antidepressants (most commonly selective serotonin reuptake inhibitors such as PROZAC or PAXIL). Anti-dementia drugs and drugs used for treating alcohol and opioid dependence were also on this list.

The classes of level 3 medications that drivers were prescribed prior to the accidents included certain opioids, other antipsychotics, other anxiolytics and hypnotics/sedatives.

The mechanisms by which medications impair driving ability vary. Some medications, such as benzodiazepines, can make a person drowsy and cause a driver to fall asleep. Diabetes drugs can cause hypoglycemia, which in severe cases can cause seizures or loss of consciousness. Other drugs can affect psychomotor and cognitive functions, impairing a driver’s judgment and reaction time.

What You Can Do

While the U.S. does not — but should — have the same system for classifying drugs into levels 0 through 3 for risk of driving impairment, labels for drugs that can impair driving ability generally include less standardized warnings about this risk.

Whenever you are prescribed a new drug, you should ask your health care provider whether the new drug alone or in combination with other drugs you are already taking can make you drowsy or impair your ability to drive in some other way, and whether it is safe to drive while taking the drug.

You should also read any Food and Drug Administration (FDA) Medication Guide available for the new drug to see if there are any advisories not to drive while taking the medication. Medication Guides can be obtained from any pharmacist or on the FDA’s website: www.fda.gov/Drugs/DrugSafety/ucm085729.htm.

If you are prescribed a new drug that has a risk of driving impairment, you should avoid driving until you have taken the new medicine for several days and have had sufficient time to assess whether the drug is causing side effects that could impair your driving ability or until you have stopped using the medication.

Because alcohol also impairs driving ability, you should avoid consuming alcohol prior to driving, especially when taking medications that have a risk of driving impairment.

If you find that a new medication does cause side effects that can impair your driving ability, you should ask your health care provider about alternative drugs or nondrug treatments.

You should not discontinue any drug without consulting with the prescriber.

Examples of classes of level 2 medications strongly associated with increased risk of driver culpability in injurious accidents

• alcoholic-dependence drugs
• anti-dementia drugs
• antidepressants (most commonly selective serotonin reuptake inhibitors such as PROZAC or PAXIL)
• antipsychotics (certain ones)
• anti-seizure drugs
• anxiolytics (tranquilizers, predominantly benzodiazepines)
• opioid-dependence drugs

Examples of classes of level 3 medications strongly associated with increased risk of driver culpability in injurious accidents

• antipsychotics (certain ones)
• anxiolytics (certain ones)
• hypnotics/sedatives
• opioids (certain ones)