Diphenhydramine

**Semantic type:** Pharmacologic Substance

**Definition:** A first generation antihistamine and ethanolamine with sedative and anti-allergic properties. Diphenhydramine competitively inhibits the histamine-1 (H1) receptor, thereby alleviating the symptoms caused by endogenous histamine on bronchial, capillary and gastrointestinal smooth muscles. This prevents histamine-induced bronchoconstriction, vasodilation, increased capillary permeability, and GI smooth muscle spasms.

**Synonyms:** - 2-(Diphenylmethoxy)-N,N-dimethylethylamine - DIPHENHYDRAMINE - FAR 90X2 - O-Benzhydryldimethylaminoethanol - PM 255 - Probedryl - Rigidyl - S51 - Syntedril - diphenhydramine