di·phen·hy·dra·mine 
(dī′fĕn-hīdrə-mēn′, -mĭn)
(dī′fĕn-hīdrə-mēn′, -mĭn)n.
A sedating antihistamine drug, C17H21NO, used usually in the form of its hydrochloride to treat symptoms of colds and allergic conditions, motion sickness, insomnia, and parkinsonism.