Diphenhydramine

Diphenhydramine hydrochloride (ˌdaɪfɛnˈhaɪdrəmiːn) is a first generation antihistamine mainly used to treat allergies. Like most other antihistamines, the drug also has a powerful hypnotic effect, and for this reason is often used as a non-prescription sleep aid and a mild anxiolytic. The drug also acts as an antiemetic. It is produced and marketed under the trade name Benadryl by McNeil-PPC (a division of Johnson & Johnson) in the U.S. and Canada, and Dimedrol in other countries. It is also found in the name-brand products Nytol, Unisom, Tylenol PM, and Advil PM though some Unisom products contain doxylamine instead. It is available as an over-the-counter (OTC) or prescribed HCl injectable. It may also be used for the treatment of extrapyramidal side effects of many antipsychotics, such as the tremors that haloperidol can cause. Additionally, injectable diphenhydramine can be used for life threatening reactions (anaphylaxis) to allergens such as bee stings, peanuts, or latex rather than risking the side effects of epinephrine. It is a member of the ethanolamine class of antihistaminergic agents.