diphenidol diphenidol diphenidol is a muscarinic antagonist employed as an antiemetic and as an antivertigo agent. it is not marketed in the united states or canada. diphenidolclinical dataahfs/drugs.commicromedex detailed consumer informationroutes ofadministrationoralatc codenonepharmacokinetic dataelimination half-life4 hoursidentifiers iupac name 1,1-di(phenyl)-4-piperidin-1-ylbutan-1-ol cas number972-02-1 ypubchem cid9175iuphar/bps7163drugbankdb01231 ychemspider2947 yuniinqo8r319lykeggd03858 ychebichebi:4638 ychemblchembl936 ycomptox dashboard (epa)dtxsid3022950 echa infocard100.012.310 chemical and physical dataformulac21h27nomolar mass309.453 g·mol−13d model (jsmol)interactive image smiles oc(c1ccccc1)(c2ccccc2)cccn3ccccc3 inchi inchi=1s/c21h27no/c23-21(19-11-4-1-5-12-19,20-13-6-2-7-14-20)15-10-18-22-16-8-3-9-17-22/h1-2,4-7,11-14,23h,3,8-10,15-18h2 ykey:ogakltjnuqrzju-uhfffaoysa-n y (verify) although the mechanism of action of diphenidol on the vestibular system has not yet been elucidated, it exerts an anticholinergic effect due to interactions with mach receptors, particularly m1, m2, m3 and m4. hence, its actions may take place at the vestibular nuclei, where a significant excitatory input is mediated by ach receptors, and also at the vestibular periphery where mach receptors are expressed at efferent synapses. a series of selective mach-receptor antagonists based on the diphenidol molecule has been synthesized, but they have not yet been the subject of clinical trials.