Ritanserin

Ritanserin is a selective antagonist of the serotonin (5-HT) receptor subtype, 5-HT_2A.¹ In a radioligand binding assay, ritanserin exhibits high selectivity for 5-HT_2A over 5-HT₁ receptors (IC₅₀s = 0.9 nM and >1000 nM, respectively).² It also demonstrates relatively low affinity for histamine H₁, dopamine D₂, α₁-adrenergic, and α₂-adrenergic receptors (39-, 77-, 107-, and 166-fold lower relative to 5-HT_2A, respectively). Ritanserin (2.5 mg/kg) is long-acting, occupying >70% of 5-HT_2A sites up to 48 hours following subcutaneous administration to rats and guinea pigs. In vivo, ritanserin (10 mg/kg) blocks 5-hydroxy tryptophan-induced head twitches in rats.³

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1. Janssen, P.A. Pharmacology of potent and selective S2-serotonergic antagonists. J. Cardiovasc. Pharmacol. 7(Suppl 7), S2-11 (1985).

2. Leysen, J.E., Gommeren, W., Van Gompel, P., et al. Receptor-binding properties in vitro and in vivo of ritanserin: A very potent and long acting serotonin-S2 antagonist. Mol. Pharmacol. 27(6), 600-611 (1985).

3. Watanabe, Y., Usui, H., Kobayashi, S., et al. Syntheses and 5-HT₂ antagonist activity of bicyclic 1,2,4-triazol-3(2H)-one and 1,3,5-triazine-2,4(3H)-dione derivatives. J. Med. Chem. 35(1), 189-194 (1992).