Ephenidine, diphenidine, and methoxphenidine complications reported to the French Addictovigilance Network.

Ephenidine, diphenidine, and methoxphenidine belong to the family of diarylethylamines that are psychoactive substances derived from lefetamine (N, N-di-methyl-1,2-diphenylethylamine, also called L-SPA). These dissociative anesthetic compounds act as potent and selective N-methyl-d-aspartate receptor antagonists and were recently classified as narcotic drugs in France. The available data suggest a significant risk of psychic and somatic complications. To obtain more information, this retrospective study analyzed all spontaneous notifications of serious cases of ephenidine, diphenidine, and methoxphenidine abuse collected by the French Addictovigilance Network from 2012 to 2016 and classified them as proven, probable, and possible. For each case, age, sex, concomitantly ingested substances, pattern of abuse of psychoactive drugs, and related complications (scored using the poisoning severity score) were collected. Eighteen cases were identified (one in 2013, five in 2015, and 12 in 2016) in 16 men (median age: 31.5 years [IQR 25-75% 27-34]). Ephenidine, diphenidine, and methoxphenidine were involved in four, seven, and 11 cases, respectively. No case was considered proven, 16 cases were considered possible, and two probable due to polysubstance abuse (co-ingestion of other new psychoactive substances). The reported clinical complications were minor in five cases, moderate in six cases, and serious in four cases, and included psychiatric, neurologic, and cardiovascular problems. This analysis indicates that the number of reported cases progressively increased from 2012 to 2016 and mainly concerned methoxphenidine. The addictive potential of these substances seems highly probable; but further investigations are needed to limit their harmful effects.

Ephenidine: A new psychoactive agent with ketamine-like NMDA receptor antagonist properties.

To avoid legislation based on chemical structure, research chemicals, frequently used for recreational purposes, are continually being synthesized. N-Ethyl-1,2-diphenylethanamine (ephenidine) is a diarylethylamine that has recently become popular with recreational users searching for dissociative hallucinogenic effects. In the present study, the pharmacological basis of its neural actions has been investigated, initially by assessing its profile in central nervous system receptor binding assays and subsequently in targeted electrophysiological studies. Ephenidine was a potent inhibitor of 3H-MK-801 binding (Ki: 66 nM), implying that it acts at the PCP site of the N-methyl-d-aspartate (NMDA) receptor. It also showed modest activity at dopamine (379 nM) and noradrenaline (841 nM) transporters and at sigma 1 (629 nM) and sigma 2 (722 nM) binding sites. In experiments of extracellular recording of field excitatory postsynaptic potentials (fEPSPs) from area CA1 of rat hippocampal slices, ephenidine, 1 and 10 µM, respectively, produced a 25% and a near maximal inhibition of the NMDA receptor mediated fEPSP after 4 h superfusion. By contrast, ephenidine (50 µM) did not affect the AMPA receptor mediated fEPSPs. In whole cell patch clamp recordings, from hippocampal pyramidal cells, ephenidine (10 µM) blocked NMDA receptor-mediated EPSCs in a highly voltage-dependent manner. Additionally, ephenidine, 10 µM, blocked the induction of long term potentiation (LTP) in CA1 induced by theta burst stimulation. The present data show that the new psychoactive substance, ephenidine, is a selective NMDA receptor antagonist with a voltage-dependent profile similar to ketamine. Such properties help explain the dissociative, cognitive and hallucinogenic effects in man. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'.