Over-The-Counter Antihistamines

The next (April 29) issue of The Medical Letter will include a short article on CNS Toxicity of First-Generation H1-Antihistamines, which was inspired by the next (May) issue of Treatment Guidelines, titled Drugs for Allergic Disorders. Antihistamines are useful medications, particularly for allergic disorders, but they can cause some problems.

In The Medical Letter we focused on the CNS toxicity of older antihistamines such as diphenhydramine (Benadryl) and chlorpheniramine (Chlortrimeton) because they are found in so many over-the-counter medications sold for relief of colds, insomnia and allergies, and the patients who take them may be totally unaware of how much they can impair CNS function and how long that impairment can persist. The most worrisome aspect of this impairment is that it can occur without symptoms of drowsiness.

Newer antihistamines such as fexofenadine (Allegra), loratidine (Claritin) or cetirizine (Zyrtec) are much less likely to cause these problems and, like the older drugs, they are all available generically and over-the-counter. They are not marketed to the same extent in heavily advertised combination products, and so they may be less familiar to many patients. The absence of sedation (cetirizine can be sedating in some patients) makes them not useful for treatment of insomnia, but better drugs with shorter half-lives are available for that indication. Not without a prescription, of course, but safety should always trump convenience.

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Comments

  1. I am using a topical regimen for postmenopausal rosacea that includes diphenhydramine HCl 2%/ Zinc acetate 0.1%. Is there any known problem with longterm use of antihistamine creams? I have found it very soothing and providing great control. After 10 years I have been able to stop oral tetracyclines and topical metronidazole. The full regimen is daily cleaning with deodorant soap and a bit of oil-based beauty bar, then twice/day using the above anti-itch cream and then Curel sustained release skin lotion. I have had relief of facial hyperemia, itching, papules, crusting, and friability. It is also inexpensive. Any responses, have others tried it?

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