What are the mechanisms of action of antihistamines for insomnia?

Updated: Sep 11, 2018
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Diphenhydramine and doxylamine are commonly used in over-the-counter insomnia medications. They exert their effect by disrupting wake-promoting histaminergic neurotransmission from the tuberomammillary nucleus by antagonism of the H1 receptor. Doxepin, mirtazapine, olanzapine, and quetiapine also exert sleep-promoting effects via this mechanism.

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