NCIt definition : An ethanolamine derivative with antihistaminic property. Phenyltoloxamine blocks H1
histamine receptors, thereby inhibiting phospholipase A2 and production of endothelium-derived
relaxing factor, nitric oxide. Subsequent lack of activation of guanylyl cyclase through
nitric oxide results in decreased cyclic GMP levels, thereby inhibiting smooth muscle
constriction of various tissues, decreasing capillary permeability and decreasing
other histamine-activated allergic reactions.;