Potent histamine H3 and H4 antagonist/inverse agonist. Ki values are 25 and 27 nM for human recombinant H3 and H4 receptors respectively. Blocks eosinophil shape change (IC50 = 1.4 μM) and chemotaxis (IC50 = 519 nM) induced by histamine. Freely crosses the blood-brain barrier. Also available as part of the Histamine H3 Receptor Tocriset?. Purity 99%. MW (observed): 292.44