H1 antagonist

noun
\ ˈāch-ˈwən- How to pronounce H{inf}1{/inf} antagonist (audio) \
variants: or H1 receptor antagonist also H1 blocker

Medical Definition of H1 antagonist

 (Entry 1 of 2)

: any of numerous drugs (such as fexofenadine or loratadine) that bind competitively with histamine to H1 receptors on cell membranes and are used to relieve allergic symptoms and variously as sedatives, antiemetics, and anticholinergics H1 antagonists prevent and relieve the sneezing, nasal and ocular itching, rhinorrhea, tearing, and conjunctival erythema of the early allergic response to antigen, but they are less effective for the nasal blockage characteristic of the late allergic reaction.— F. Estelle R. Simons and Keith J. Simons, The New England Journal of Medicine, 9 June 1994

H1 receptor

noun

Medical Definition of H1 receptor (Entry 2 of 2)

: a receptor for histamine on cell membranes that modulates the dilation of blood vessels and the contraction of smooth muscle — see h1 antagonist

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