What is the role of antihistamines in the treatment of insomnia?

Updated: Sep 11, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Antihistamines are the major ingredient of over-the-counter (OTC) sleep aids and are the ingredient in cold and sinus formulas sold as bedtime-use medications. Nevertheless, common antihistamines (ie, first-generation H1-receptor antagonists such as diphenhydramine, hydroxyzine, and doxylamine) are not indicated for the treatment of sleeplessness.

Zhang et al reported that a nighttime dose of 50 mg diphenhydramine resulted in a next-day residual sedative effect. This double-blind, placebo-controlled, crossover study used positron emission tomography (PET) for an objective measurement of residual effect. [91]

While H1 antihistamines have sedative effects in healthy individuals, no study has established an effective dose range for these agents’ hypnotic effect in patients with insomnia. These agents may have some subjective benefit, but long-term efficacy and safety have not been demonstrated. Thus, their regular use in individuals with insomnia is not advised. [6]

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