Pirdonium bromide is a hydrophilic H1 receptor ligand with quaternary ammonium group[1].
References
[1] Hishinuma S, et al. Ca2+ -dependent down-regulation of human histamine H1 receptors in Chinese hamster ovary cells. J Neurochem. 2018 Jan;144(1):68-80. DOI:10.1111/jnc.14245
