Oxomemazine is a phenothiazine-based histamine H1-receptor blocker with pronounced antimuscarinic properties. Oxomemazine is a selective antagonist for muscarinic M1 receptor, displays about 20-fold difference in the affinity for high (Ki = 84 nM, M1 receptor) and low (Ki = 1.65 μM, M2 receptor) affinity sites. Oxomemazine?an antihistamine and anticholinergic agent used for the study of cough treatment[2].