Fananserin (RP 62203) is an orally bioavailable, potent and selective 5-hydroxytryptamine2 (5-HT₂) receptor antagonist, with a K_i of 0.37 nM for the rat 5-HT_2A receptor. Fananserin also is a selective dopamine D4 receptor antagonist, with a K_i of 2.93 nM for the human dopamine D4 receptor^[1]. IC50 & Target: Ki: 0.37 nM (5-HT₂), 2.93 nM (human DA D4 receptor)^[1] In Vitro: Fananserin is relatively selective for 5-HT₂ receptor, having lower affinity for the 5-HT_1A receptor and very low affinity for the 5-HT₃ receptor^[1].
Fananserin displaces [³H]spiperone binding to recombinant human dopamine D 4 receptors with a K_i of 2.93 nM^[1].
RP 62203 displays low to moderate affinity for α1-adrenoceptors, dopamine D2 receptors and histamine H ₁ receptors^[2].
In Vivo: Fananserin displaces ^[125I]AMIK from 5-HT₂ receptors with an IC₅₀ of 0.21 nM in rat frontal cortex^[2].
Fananserin shows moderate affinity for alpha 1-adrenoceptors in the rat thalamus (IC₅₀ = 14 nM) and for histamine H1 receptors in the guinea-pig cerebellum (IC₅₀ = 13 nM)^[2].
Fananserin (0.5-4 mg/kg; p.o.) increases the duration of deep nonrapid eye movement (NREM) sleep at the expense of wakefulness in a dose-dependent manner^[3].