What is Diphen?
Diphenhydramine (; abbreviated DPH, sometimes DHM) is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms. The drug has a strong hypnotic effect and is FDA-approved as a nonprescription sleep aid, especially in the form of diphenhydramine citrate. It is produced and marketed under the trade name Benadryl by McNeil-PPC (a division of Johnson & Johnson) 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 or store brand medication.
Diphenhydramine was one of the first antihistamines developed in the late 1940s and is the prototype of the ethanolamine class of first-generation antihistamines, which also includes orphenadrine, phenyltoloxamine, doxylamine, and halogenated diphenhydramine derivatives.