NCIt definition : A synthetic ethanolamine with anticholinergic, sedative, and histamine H1 antagonistic
properties. Clemastine fumarate blocks the H1 histamine receptor and prevents the
symptoms that are caused by histamine activity on capillaries, bronchial and gastrointestinal
smooth muscles, including vasodilation, increased capillary permeability, bronchoconstriction,
and spasmodic contraction of gastrointestinal smooth muscles. This drug also prevents
histamine-induced pain and itching of mucous membranes.;