Cyclizine is a histamine H1 receptor antagonist.1,2,3 It binds selectively to histamine H1 receptors (Kd = 5 nM) over H2 and H3 receptors (Kds = 1,600 and >580 nM, respectively).3 Cyclizine inhibits anti-IgE-induced histamine release from isolated human lung fragments with an IC50 value of 5.42 µM but induces histamine release with a 50% release concentration (RC50) of 10.81 µM.4 It reduces LPS-induced nitrite accumulation and protein levels of induced nitric oxide synthase (iNOS) in RAW 264.7 cells when used at a concentration of 100 nM.2 Cyclizine (10 and 20 mg/kg) reduces immobility in the forced swim test in rats.5
1.Hamlin, K.E., Weston, A.W., Fischer, F.E., et al.Histamine antagonists. II.1 Unsymmetrical 1,4-disubstituted piperazinesJ. Am. Chem. Soc.71(8)2731-2734(2019) 2.KrÁlovÁ, J., Ra?kovÁ, L., PekarovÁ, M., et al.The effects of H1-antihistamines on the nitric oxide production by RAW 264.7 cells with respect to their lipophilicityInt. Immunopharmacol.9(7-8)990-995(2009) 3.Hill, S.J.Distribution, properties, and functional characteristics of three classes of histamine receptorPharmacol. Rev.42(1)45-83(1990) 4.Church, M.K., and Gradidge, C.F.Inhibition of histamine release from human lung in vitro by antihistamines and related drugsBr. J. Pharmacol.69(4)663-667(2019) 5.Khanwelkar, C.C., Gokhale, D.V., Santakke, A.V., et al.Effects of H1-receptor antagonists in antidepressant tests in ratsAl Ameen J. Med. Sci.1(2)84-92(2008)