Diphenidine (1,2-DEP, DPD, DND) is a dissociative anesthetic that has been sold as a
designer drug. The synthesis of diphenidine was first reported in 1924, and employed a Bruylants reaction analogous to the one that would later be used to discover phencyclidine in 1956. arylcyclohexylamines, diphenidine and the related compound methoxphenidine became available on the grey 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. In dogs diphenidine exhibits greater antitussive potency than codeine phosphate.