Ciproxifan(FUB-359) is a highly potent and selective histamin H3-receptor antagonist with IC50 of 9.2 nM, with low apparent affinity at other receptor subtypes. IC50 value: 9.2 nM(Ki) Target: H3 receptor In vitro, Ciproxifan behaved as a competitive antagonist at the H3 autoreceptor controlling 3H histamine release from synaptosomes and displayed similar Ki values (0.5-1.9 nM) at the H3 receptor controlling the electrically-induced contraction of guinea pig ileum or at the brain H3 receptor labeled with 125I-iodoproxyfan. This appears to be an orally bioavailable, extremely selective and potent H3-receptor antagonist whose vigilance- and attention-promoting effects are promising for therapeutic applications in aging disorders.