Study finds hay-fever medication worse than alcohol in impairing driver skills

March 6, 2000
Web posted at: 5:50 p.m. EST (2250 GMT)

From staff reports

ATLANTA (CNN) -- Motorists using over-the-counter remedies to fight colds and hay fever may be a greater risk for causing traffic collisions than drunken drivers, according to a study at the University of Iowa.

Researchers focused on the drowsiness caused by Benadryl, a medication commonly taken for sniffles and sneezes. Bendadryl contains diphenhydramine, which is used to treat allergies, colds, rashes and to ease postoperative nausea and vomiting.

"First-generation antihistamines such as diphenhydramine are known to affect driving performance," said Dr. John M. Weiler, professor of internal medicine at the university and lead author of the study. "However, we were surprised to find that this antihistamine has more impact on driving performance that alcohol does."

Weiler and his associates studied 40 licensed drivers, ages 25 to 44, who had hay fever -- allergies to ragweed pollen -- and who had previously used antihistamines to treat the problem. Hay fever affects about 40 million Americans.

The drivers, tested once a week for five weeks, were divided into four groups. Each was given one dose of Benadryl (50 milligrams), Allegra (fexofenadine) 60 milligrams, a placebo or alcohol.

The researchers said the subjects' alcohol consumption was sufficient to cause 0.10 percent blood-alcohol concentration, a level defined in many states as drunken driving. (One researcher noted that more than half of the states also have laws prohibiting driving under the influence of sedating medications.)

Drivers treated with fexofenadine or placebo had no problem driving, the researchers concluded. Those who used alcohol showed a poorer driving performance.

"After participants took diphenhydramine, driving performance was poorest, indicating that diphenhydramine had a greater impact on driving than alcohol did," said the report, published this week in Annals of Internal Medicine. The peer- reviewed journal is published by the American College of Physicians-American Society of Internal Medicine, the largest medical specialty organization in the United States.

Of particular interest to users of Benadryl, the researchers found that "drowsiness ratings were not a good predictor of impairment," suggesting that drivers receiving antihistamines may not be able to judge accurately when they are impaired.

Participants in the study were tested on a computer-assisted driving simulator. The study was supported in part by grants from the National Institutes of Health and from Hoechst Marion Roussel Inc., a company now called Aventis Pharmaceuticals Inc. It makes Allegra, which fared well in the study.

A statement from Warner-Lambert Co., maker of Benadryl, quotes an editorial in the journal that "the possibility that the effects seen in experimental settings ... do not translate into an increased risk for motor-vehicle crashes in real life."

Nonetheless, the editorial writers -- Sean Hennessy, who holds a doctorate of pharmacology, and Brian Strom, a physician, both of the University of Pennsylvania School of Medicine -- conclude that "non-sedating antihistamines should generally be preferred over sedating antihistamines in patients who drive."

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RELATED SITES:

University of Iowa
Living With Allergies -- Fact Sheet
American College of Physicians-American Society of Internal Medicine
Warner-Lambert Co.
Allegra - Aventis Pharmaceuticals Inc.

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