N-Methylhistaprodifen Dioxalate Salt is a highly active and potent histamine H1-receptor agonist. N-Methylhistaprodifen dioxalate salt is more potent than a histamine by a factor of 3.5 on guinea pig ileum and more potent than histamine by a factor of 4.3 on guinea pig arterial H1-receptor-mediated vasoconstriction. It is the most potent H1-receptor agonist on the guinea pig ileum out of 17 agonists tested. It does not stimulate H2 and H3 histamine receptors and has potential use in the study of H1-receptor-mediated physiological and pathophysiological functions. Molecular Formula: C21H25N3 ?2C2H2O4 Molecular Weight: 319.44180069999999