Diphenhydramine

Diphenhydramine (DPH) is an antihistamine medication. It is mainly used to treat allergies. It can also be used to treat insomnia, the common cold, tremor in parkinsonism, and nausea. It is taken by mouth, injected into a vein, injected into a muscle, or put on the skin. It works best two hours after taking, and works for up to seven hours.
Common side effects include sleepiness, bad balance and a bad stomach. It should not be used in young children or the elderly. It can be used while pregnant, but not when breastfeeding. It works by blocking some effects of histamine from working at the H1 receptor. Diphenhydramine is also an anticholinergic, and is a deliriant at high doses.
Diphenhydramine was first made by George Rieveschl and was first used in 1946. It is available as a generic medication. It is also sold under the brand name Benadryl, as well as others. It was the 241st most commoly prescribed medication in the United States in 2017.