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Allergies Health Center

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New Antihistamines: Not So Nonsedating?

Review of 18 Studies Shows "Blurred" Difference Compared With Older Allergy Drugs


"They found the people taking Allegra or placebo drove well. The people who were intoxicated drove as though they were. And the people who took Benadryl looked normal, but drove like the drunks," says Steven H. Cohen, MD, an allergist in Milwaukee who serves as spokesman for the American Academy of Allergy, Asthma and Immunology. That study was sponsored by the company that manufactures Allegra.

Still, Cohen says what makes it important is that it had patients perform a technical skill that requires optimal alertness. "And based on that study, I certainly wouldn't have wanted to face those Benadryl people on the road." In Bender's analysis, some studies involved self-reported levels of sedation, while others measured their ability to perform specific tasks.

"Obviously, in the old days when you only had sedating antihistamines, that's what you used, but you generally start out by having patients take them at bedtime. And in many cases, over time the sedation became less of a problem, so they were able to take them twice a day," Cohen tells WebMD. "Today, most people would lead to nonsedating medications."

And perhaps with good reason: Some 35 states in the U.S. have laws related to driving while impaired -- not only by alcohol, but also from antihistamines, says Cohen. These laws also apply to nonsedating formulas.

"Zyrtec is a relatively non-sedating antihistamine, but it has a warning in the Physician's Desk Reference [which gives detailed information on prescribing drugs] about operating machinery when taking it," he tells WebMD. "There's no question that even the nonsedating antihistamines can be sedating in some people."

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