Histamine H1 receptor antagonists work by blocking the histamine H1 receptor, a mechanism of action different than that of any other medication for the treatment of insomnia. Administration of first-generation H1 receptor antagonists—chlorpheniramine (4.2. 1), diphenhydramine (4.2. 2), pyrilamine (4.2.

How does H1 receptor work?

The H1-receptor drives cellular migration, nociception, vasodilatation, and bronchoconstriction (39), whereas the H2-receptor modifies gastric acid secretion, airway mucus production, and vascular permeability (40). The H3-receptor plays an important role in neuro-inflammatory diseases (37).

Why do H1 antagonists cause sedation?

First-generation antihistamines block peripheral H1 receptors, but also cross the blood – brain barrier and block central nervous system H1 and cholinergic receptors as well. This produces the unwanted side effect of sedation.