Ciproxifan hydrochloride (FUB 359) is an effective, selective, orally active, and competitive antagonist of the histamine H3-receptor, exhibiting an IC50 value of 9.2 nM. This compound demonstrates low apparent affinity for other receptor subtypes. Ciproxifan hydrochloride is utilized in research related to age-related diseases and Alzheimers disease.

Ciproxifan hydrochloride effectively suppresses the release of [3H]HA from rat cerebral cortex synaptosomes, exhibiting a K i of 0.5 nM. Additionally, at concentrations ranging from 0.01 nM to 1 μM over 60 minutes, it inhibits the binding of [125I]iodoproxyfan to rat striatal membranes, with a K i determined to be 0.7 nM.

Administered at a dosage of 1 mg/kg orally, ciproxifan hydrochloride elevates t-MeHA levels in the mouse brain with an effective dose (ED 50) of 0.14 mg/kg. When administered intraperitoneally at 3 mg/kg, it enhances response accuracy in rats performing a five-choice task, but only when the stimulus duration is reduced to 0.25 seconds from 0.50 seconds. At dosages ranging from 0.15 to 2 mg/kg orally, ciproxifan hydrochloride significantly activates the neocortical electroencephalogram in cats, increasing fast-rhythm density and inducing nearly total wakefulness. Additionally, a single intravenous dose of 1 mg/kg reduces H3-receptor ligand concentrations in mouse serum, displaying half-lives of 13 minutes for distribution and 87 minutes for elimination. This compound also shows an oral bioavailability (F=62%) and reaches a maximal concentration (C max =420 nM) in mice when given orally at 1 mg/kg.