Diphenidine (1-(1,2-diphenylethyl)piperidine) is a dissociativeanesthetic drug that has been sold online as a research chemical. The synthesis of diphenidine was first reported in 1924, and employed a nitrile displacement reaction analogous to the one that would later be used to discover phencyclidine in 1956. Shortly after the 2013 UK ban on arylcyclohexylamines, diphenidine and the related compound methoxphenidine became available on the gray market. Anecdotal reports describe high doses of diphenidine producing "bizarre somatosensory phenomena and transient anterograde amnesia." Diphenidine and related diarylethylamines have been studied in vitro as treatments for neurotoxic injury and are antagonists of the NMDA receptor. Though vendors of diphenidine have stated the compound "acts on dopamine transport" to date diphenidine has not been screened for affinity at the dopamine transporter. In dogs diphenidine exhibits greater antitussive potency than codeine phosphate.
^EP 0346791, Gray NM, Cheng BK, "1,2-diarylethylamines for treatment of neurotoxic injury"
^Berger, M. L.; Schweifer, A.; Rebernik, P.; Hammerschmidt, F. (2009). "NMDA receptor affinities of 1,2-diphenylethylamine and 1-(1,2-diphenylethyl)piperidine enantiomers and of related compounds". Bioorganic & Medicinal Chemistry17 (9): 3456. doi:10.1016/j.bmc.2009.03.025.edit