Like the end of most holiday weekends, traffic is going to be extra tough, and increased accidents are expected.  Drinking and driving is a well known risk.  But one study identified another risk for accidents:  a common ingredient in many over-the-counter allergy medicines used by millions might impair drivers even more than liquor (Annals of Internal Medicine, 2001).  After testing 40 allergy sufferers in a driving simulator, researchers found that the standard dose of the antihistamine in Benadryl™ and similar medicines had a greater effect than a few drinks on driving "coherence," or the ability to match the speed of the vehicle ahead.

This common antihistamine, diphenhydramine, also had an effect similar to alcohol on impaired steering stability and the likelihood of crossing into the oncoming lane.  This study did not address the effects of combining alcohol and antihistamines, but that is well known to be even more sedating.

Antihistamines are not the only medicines which cause drowsiness or impair a driver's response time or vehicle control.  Whenever taking a new medicine, ask your doctor or pharmacist about whether it is safe for you to drive.  And don't ask from your cell phone while driving.  Cell phone usage by drivers increases the risk of motor vehicle accidents by 4 times. . .even when no alcohol or drugs are on board.

Have a safe holiday!

Created: 5/28/2001  -  Donnica Moore, M.D.