Antihistamines - The Changing World Of Allergy Treatments: Allergies

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Antihistamines

Antihistamines

Antihistamines remain the most common treatment for allergic rhinitis. They are also valuable in relieving itch and so are the cornerstone of treatment of hives. Antihistamines block the action of histamine, a major cause of your runny nose, sneezing, and itchy eyes. Many people who suffer from even mild seasonal allergic rhinitis (hay fever) are familiar with the older antihistamines and their groggy, mind-numbing effect. But the days of having to either sniffle in misery or feel like a zombie are over, thanks to the newer generation of antihistamines, which are less likely to cause drowsiness. These medications also last longer than the first generation of antihistamines, which means they need to be taken only once a day instead of every four to six hours.

Drowsiness is a major problem for allergy sufferers, not just those who are driving a car or handling machinery, but also for workers and schoolchildren who can’t stay awake on the job or in school. The effect of the first-generation sedating antihistamines — for example, Benadryl or Chlor-Trimeton — has been compared to the effect of alcohol when driving a car. Alcohol, even when within legal limits, impairs driving judgment to some degree. Researchers decided to compare the older antihistamines with the newer ones by observing drivers who had taken one or the other. The study showed that a 50-mg dose of diphenhydramine (Benadryl) impaired driving performance, whether or not the subjects felt drowsy. Drivers who took the standard 60-mg dose of fexofenadine (Allegra), a second-generation antihistamine, had no impairment. But less sedating doesn’t mean the newer medications have no sedating effect at all. If you increase the recommended dose, you risk drowsiness. Most of the second-generation antihistamines are available by prescription only, with the exception of Claritin, which is available over the counter.

Choosing your antihistamine First-generation (older) antihistamines* brompheniramine (Dimetane-DC) carbinoxamine (Mooredec, Rondamine, Rondec) chlorpheniramine (Allerest, Chlor-Trimeton, Deconamine) clemastine (Tavist) cyproheptadine (Periactin syrup) dimenhydrinate (Dramamine) diphenhydramine (Benadryl) doxylamine (Unisom) hydroxyzine (Atarax) meclizine (Antivert) promethazine (Phenergan) triprolidine (Actifed) *Many available over the counter Second-generation (newer) antihistamines** acrivastine (Semprex-D) azelastine (Astelin) cetirizine (Zyrtec) desloratadine (Clarinex) fexofenadine (Allegra) loratadine (Claritin, Alavert) **As of 2005, only Claritin available without a prescription

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Last updated:	August 21, 2006
Reviewed By:	Faculty of Harvard Medical School

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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