What is "diphenhydramine"

n. An antihistamine and sedative drug that blocks the effect of histamine at H1 receptor sites, reducing smooth muscle contraction.

n. antihistamine (trade name Benadryl) used to treat allergic reactions involving the nasal passages (hay fever) and also to treat motion sickness [syn: Benadryl]

Diphenhydramine (DPH, DHM) is a first-generation antihistamine mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms. The medication has a sedating effect and is FDA-approved as a nonprescription sleep aid. It possesses anticholinergic, antitussive, antiemetic, and sedative properties.

Diphenhydramine was first synthesized by George Rieveschl and first made publicly available through prescription in 1946. Diphenhydramine is marketed under the trade name Benadryl by McNeil Consumer Healthcare in the U.S., Canada, and South Africa (trade names in other countries include Dimedrol, Daedalon, and Nytol). It is also available as a generic medication.