cloperastine cloperastine cloperastine (inn) or cloperastin, in the forms of cloperastine hydrochloride (jan) (brand names hustazol, nitossil, seki) and cloperastine fendizoate (or hybenzoate), is an antitussive and antihistamine that is marketed as a cough suppressant in japan, hong kong, and in some european countries. it was first introduced in 1972 in japan, and then in italy in 1981. cloperastineclinical dataother namesht-11ahfs/drugs.cominternational drug namesroutes ofadministrationoralatc coder05db21 (who) identifiers iupac name 1-ethyl]piperidine cas number3703-76-2 ypubchem cid2805drugbankdb09002 nchemspider2703 yunii69m5l7bxekkeggd03557 ychemblchembl415087 ycomptox dashboard (epa)dtxsid7048532 echa infocard100.020.948 chemical and physical dataformulac20h24clnomolar mass329.87 g·mol−13d model (jsmol)interactive image smiles clc1ccc(cc1)c(occn2ccccc2)c3ccccc3 inchi inchi=1s/c20h24clno/c21-19-11-9-18(10-12-19)20(17-7-3-1-4-8-17)23-16-15-22-13-5-2-6-14-22/h1,3-4,7-12,20h,2,5-6,13-16h2 ykey:flnxbvjlpjnosi-uhfffaoysa-n y ny (what is this?) (verify) side effects adverse effects may include sedation, drowsiness, heartburn, and thickening of bronchial secretions. pharmacology the precise mechanism of action of cloperastine is not fully clear, but several different biological activities have been identified for the drug, of which include: ligand of the σ1 receptor (ki = 20 nm) (likely an agonist), girk channel blocker (described as "potent"), antihistamine (ki = 3.8 nm for the h1 receptor), and anticholinergic. it is thought that the latter two properties contribute to side effects, such as sedation and somnolence, while the former two may be involved in or responsible for the antitussive efficacy of cloperastine. synthesis synthesis: patents: isomers: china: the halogenation of 4-chlorobenzhydrol (1) with phosphorus tribromide in tetrachloromethane gives 1-(bromophenylmethyl)-4-chlorobenzene (2). treatment with ethylenechlorohydrin (2-chloroethanol) (3) gives 1-(4-chlorobenzhydryl)oxy-2-chloroethane (4). reaction with piperidine (5) completes the synthesis of cloperastine (6).