An extremely potent, high affinity agonist at H3 and H4 receptors (Ki values are 0.3 and 2.7 nM respectively). Induces shape change in eosinophils with an EC50 of 25 nM. Centrally active following systemic administration. Also available as part of the Histamine H3 Receptor Tocriset?. Purity 98%. MW (observed): 332.06