Trimeprazine is a histamine H1 receptor antagonist (Ki = 0.72 nM in a radioligand binding assay).1 It is selective for the histamine H1 receptor over muscarinic acetylcholine receptors (mAChRs; Ki = 38 nM in a radioligand binding assay). Trimeprazine inhibits anti-IgE-induced histamine release from isolated human lung fragments (IC50 = 19 nM) but induces histamine release with a 50% release concentration (RC50) of 1.03 ?M.2 It reduces severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication in SARS-CoV-2-infected Vero E6 cells (EC50 = 1.76 ?M) with a 50% cytotoxic concentration (CC50) value of 19.73 ?M.3 Formulations containing trimeprazine have been used in the treatment of allergic pruritis and motion sickness.
1.Kubo, N., Shirakawa, S., Kuno, T., et al.Antimuscarinic effects of antihistamines: Quantitative evaluation by receptor-binding assayJpn. J. Pharmacol.43(3)277-282(1987) 2.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) 3.Yang, L., Pei, R.-J., Li, H., et al.Identification of SARS-CoV-2 entry inhibitors among already approved drugsActa Pharmacol. Sin.42(8)1347-1353(2020)