phenbenzamine phenbenzamine phenbenzamine, sold under the brand name antergan and known by the former developmental code name rp-2339, is an antihistamine of the ethylenediamine class which also has anticholinergic properties. it was introduced in 1941 or 1942 and was the first antihistamine to be introduced for medical use. soon following its introduction, phenbenzamine was replaced by another antihistamine of the same class known as mepyramine (pyrilamine; neoantergan). following this, other antihistamines, such as diphenhydramine, promethazine, and tripelennamine, were developed and introduced. owing to their sedative effects, phenbenzamine and promethazine were assessed in the treatment of manic depression in france in the 1940s and were regarded as promising therapies for such purposes. whereas phenbenzamine was the first clinically useful antihistamine, piperoxan was the first compound with antihistamine properties to be discovered and was synthesized in the early 1930s. phenbenzamineclinical datatrade namesanterganother namesrp-2339drug classantihistamine; h1 receptor antagonistidentifiers iupac name n-(2-dimethylaminoethyl)-n-benzylaniline cas number961-71-7 ypubchem cid13751chemspider13155 yunii733w48ng2qcomptox dashboard (epa)dtxsid3043863 chemical and physical dataformulac17h22n2molar mass254.377 g·mol−13d model (jsmol)interactive image smiles cn(c)ccn(cc1ccccc1)c2ccccc2 inchi inchi=inchi=1s/c17h22n2/c1-18(2)13-14-19(17-11-7-4-8-12-17)15-16-9-5-3-6-10-16/h3-12h,13-15h2,1-2h3 ykey:chobrhhoyqkcou-uhfffaoysa-n y chemistry synthesis phenbenzamine can be prepared by the reaction of n-benzylaniline with 2-chloroethyldimethylamine. phenbenzamine synthesis