Diphenhydramine hydrochloride is an antihistamine with drying (anticholinergic) and sedative effects. It works by competing with histamine for receptor sites on target cells, blocking histamine’s effects.
In its injectable form, Benadryl has a rapid onset of action. Diphenhydramine hydrochloride is widely distributed throughout the body, including the central nervous system (CNS). Some of the drug is excreted unchanged in the urine, while the rest is metabolized by the liver.