Ephenidine

# Research Output: Ephenidine

**PSX ID:** PSX-0178  
**Research Date:** 2026-05-03  
**Substance Readiness:** Sparse/emerging — primary literature limited to a single dedicated pharmacology paper; most data from class-level studies and forensic reports.

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## Chemical Identity

**Verified against PubChem CID 110821:**

| Property | Value | Source |
|---|---|---|
| IUPAC name | N-ethyl-1,2-diphenylethanamine | PubChem CID 110821 |
| Synonyms | NEDPA, EPE | [Ref 10], [Ref 16] |
| CAS (freebase) | 60951-19-1 | ChemicalBook |
| CAS (HCl salt) | 6272-97-5 | ChemicalBook |
| PubChem CID | 110821 | PubChem |
| Molecular formula | C₁₆H₁₉N | PubChem (api_verified) |
| Molecular weight | 225.33 g/mol | PubChem (api_verified) |
| Canonical SMILES | CCNC(CC1=CC=CC=C1)C2=CC=CC=C2 | PubChem REST API |
| InChI | InChI=1S/C16H19N/c1-2-17-16(15-11-7-4-8-12-15)13-14-9-5-3-6-10-14/h3-12,16-17H,2,13H2,1H3 | PubChem REST API |
| InChIKey | IGFZMQXEKIZPDR-UHFFFAOYSA-N | PubChem (api_verified) |
| Chemical class | 1,2-Diarylethylamine | [Ref 1], [Ref 16] |

**Physical properties:**
- HCl salt melting point: 236–238 °C (solid form) [ChemicalBook, web_retrieved]
- Boiling point, solubility, logP: not located in published literature — **FLAG for editorial review**
- Appearance: described as a "neat solid" (HCl salt) in supplier data

**Stereochemistry:** Ephenidine possesses one chiral center at C1 (the carbon adjacent to the nitrogen). The PubChem isomeric SMILES contains no stereodescriptors, confirming it is commercially distributed as a **racemic mixture**. No published study has specifically evaluated the enantioselective pharmacology of ephenidine itself. However, the structural analog diphenidine (the N-deethylated metabolite of ephenidine) shows dramatic enantioselectivity at the NMDA receptor: the (S)-enantiomer displays ~40-fold higher affinity (Ki = 0.13 µM) than the (R)-enantiomer (Ki = 5.25 µM) (Wallach et al. 2016 [Ref 2]). A 2025 chiral separation paper documents analytical methods for separating diphenidine-derived NPS enantiomers [Ref 22]. **FLAG: ephenidine-specific enantiomeric pharmacology data absent; only structural analog inference available.**

**Discrepancies with seed data:** The seed data listed SMILES, InChIKey, molecular formula, and PubChem CID as blank. All four have now been confirmed from PubChem. The IUPAC name, systematic name, and molecular formula in the seed data are accurate.

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## Pharmacology

### Receptor Binding Profile

All binding data from Kang et al. (2017) [Ref 1], the only published primary pharmacology study of ephenidine. Assays conducted in rat brain membrane preparations.

| Target | Ki (nM) | Notes |
|---|---|---|
| NMDA receptor (PCP/MK-801 site) | 66 | ³H-MK-801 displacement |
| Dopamine transporter (DAT) | 379 | Reuptake inhibition |
| Noradrenaline transporter (NET) | 841 | Reuptake inhibition |
| Sigma-1 receptor | 629 | |
| Sigma-2 receptor | 722 | |
| AMPA receptor | No effect at 50 µM | Selective NMDA antagonism confirmed |

The 66 nM affinity at the NMDA PCP site is comparable to ketamine (Ki ~500 nM) but with a narrower absolute window; the compound is considerably more potent at the NMDA channel than either the DAT or NET, making NMDA antagonism the dominant pharmacological action (Kang et al. 2017 [Ref 1]).

### Mechanism of Action

Ephenidine is an **uncompetitive, voltage-dependent open-channel blocker** of the NMDA receptor (Kang et al. 2017 [Ref 1]), acting at the PCP binding site within the ion channel pore. This mechanism is identical to ketamine and phencyclidine. Key electrophysiological findings in rat hippocampal slices (Kang et al. 2017 [Ref 1]):

- 1 µM produced ~25% inhibition of NMDA receptor-mediated fEPSPs in CA1 after 4h superfusion
- 10 µM produced near-maximal inhibition under the same conditions
- 50 µM produced **no effect** on AMPA receptor-mediated fEPSPs, confirming NMDA selectivity
- 10 µM blocked NMDA receptor-mediated EPSCs in hippocampal pyramidal cells in a **highly voltage-dependent manner** (whole-cell patch clamp)
- 10 µM blocked LTP induction in CA1 by theta burst stimulation, consistent with NMDA receptor-dependent synaptic plasticity disruption

The voltage-dependent block profile is described as "similar to ketamine" [Ref 1]. This contrasts with memantine, which has faster unblocking kinetics and is better tolerated at therapeutic doses.

The weak activity at DAT (379 nM) and NET (841 nM) confers secondary norepinephrine-dopamine reuptake inhibition properties, which contribute to stimulant-like components of the subjective effect profile (Kang et al. 2017 [Ref 1]; Wallach & Brandt 2018 [Ref 16]).

Sigma receptor affinities (sigma-1: 629 nM; sigma-2: 722 nM) are in a pharmacologically relevant range but their contribution to subjective effects remains uncharacterized for this compound.

**No data available:** EC50 values for functional endpoints, in vivo receptor occupancy data, human receptor binding, opioid receptor binding (relevant given lefetamine's opioid activity — not measured in [Ref 1]).

### Pharmacokinetics

**Human pharmacokinetic studies: none published.** All PK data derives from rat urine studies [Refs 10, 11].

**Metabolic pathways** (from Wink et al. 2014 [Ref 10], rat urine):

1. **N-dealkylation** — primary route; cleaves the N-ethyl group to produce diphenidine (N-deethyl-NEDPA), which is itself a pharmacologically active NMDA antagonist (Ki ~50–130 nM) [Refs 2, 13]
2. **Mono- and bis-hydroxylation** of the benzyl ring, followed by methylation of one hydroxyl group
3. **Hydroxylation** of the phenyl ring (after N-dealkylation)
4. **Glucuronidation and sulfation** of hydroxylated metabolites (Phase II)

Key metabolites identified in rat urine: N-deethyl-NEDPA (diphenidine), N-deethyl-hydroxy-NEDPA, hydroxy-NEDPA, hydroxy-methoxy-NEDPA [Ref 10]. Parent compound is not detectable at 0.3 mg/kg dose in rat urine — only metabolites are recovered, suggesting extensive first-pass metabolism or rapid systemic metabolism.

**CYP enzyme contributions** to N-dealkylation (relative activity factor approach, human microsomes; Wink et al. 2015 [Ref 11]):
- CYP2B6: 30%
- CYP1A2: 27%
- CYP2C19: 23%
- CYP3A4: 17%
- CYP2D6: 4%

Because four or more CYP enzymes contribute to the primary metabolic step, the risk of clinically significant CYP-mediated drug-drug interactions is assessed as **low** [Ref 11]. However, this finding pertains only to the primary N-dealkylation step; interactions at downstream CYP-mediated hydroxylation steps have not been evaluated.

**Half-life:** The seed data proposes a 5-day tolerance half-life and 1.5-week full reset. No published pharmacokinetic data confirms a specific elimination half-life for ephenidine or its metabolites in humans. This value is unverified. **FLAG: tolerance half-life is seed data, not confirmed by published sources.**

**Bioavailability, Tmax, plasma protein binding:** Not published.

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## History

### Origins in Pharmaceutical Chemistry

Ephenidine's structural scaffold — the N-alkyl-1,2-diphenylethylamine — first appeared in pharmacological literature in the 1940s. Tainter et al. (1943) and Goodson et al. (1946) investigated N-alkylated 1,2-diphenylethylamines in analgesic research contexts [per Wikipedia 1,2-diarylethylamine article and Wink et al. 2015 [Ref 12]; primary sources not independently verified — unverifiable due to pre-digital publication]. The pharmaceutical parent compound **lefetamine** (N,N-dimethyl-1,2-diphenylethylamine, L-SPA) was marketed as an opioid analgesic in Japan and Italy in the 1940s–1950s before being controlled due to abuse liability (Wink et al. 2015 [Ref 12]). Lefetamine is structurally the N,N-dimethyl homolog of diphenidine and the N-methyl homolog relative to the diarylethylamine scaffold shared with ephenidine.

### First Appearance as Designer Drug

N-Ethyl-1,2-diphenylethylamine (NEDPA / ephenidine) was **first confiscated as a designer drug in Germany in 2008** — the earliest documented occurrence in a forensic context (Wink et al. 2014 [Ref 10]). The compound was identified alongside N-isopropyl-1,2-diphenylethylamine (NPDPA) in the same seizure.

### Market Emergence

Ephenidine's recreational use did not become widespread until approximately **2013**, when it emerged on the online NPS ("research chemical") market following UK scheduling actions against arylcyclohexylamines (Wallach & Brandt 2018 [Ref 16]). Its appearance — alongside diphenidine and methoxphenidine — was driven by demand for dissociative experiences and circumvention of existing legislation (Kang et al. 2017 [Ref 1]).

The first cases of ephenidine-related clinical complications were reported to the French Addictovigilance Network starting in 2013 (a single case), with numbers increasing substantially in 2015–2016 (Eiden et al. 2018 [Ref 9]).

### Key Research Milestones

- **2008**: First forensic confiscation, Germany
- **2013**: Emergence on NPS market; first French Addictovigilance case
- **2014**: First metabolism study (rat urine, Wink et al. [Ref 10])
- **2015**: CYP enzyme profile established (Wink et al. [Ref 11]); Sweden scheduling
- **2016**: UK Psychoactive Substances Act; Canadian scheduling; Wallach et al. diphenidine class pharmacology [Ref 2]
- **2017**: Kang et al. primary pharmacology paper published [Ref 1]; methoxphenidine use disorder case report [Ref 20]
- **2018**: French Addictovigilance comprehensive analysis [Ref 9]; Wallach & Brandt class review [Ref 16]
- **2021**: WHO 43rd ECDD adds diphenidine (not ephenidine) to Schedule II, UN 1971 Convention
- **2024 (March 20)**: UK Misuse of Drugs Act Class B scheduling (SI 2024/190)
- **2024 (October)**: Australia Schedule 9 scheduling
- **2025**: Corkery et al. systematic review of diarylethylamine deaths [Ref 8]

### Discovery/Synthesis Attribution

No academic research group synthesized ephenidine as a novel compound for medical development. As with many diarylethylamine NPS, its emergence on the recreational market appears to derive from online community synthesis discussions based on the structural template of lefetamine, without formal academic precedent for the specific compound (Wallach & Brandt 2018 [Ref 16]). Synthesis proceeds via reductive amination of benzaldehyde and styrene oxide or related Leuckart reaction routes (per class synthesis descriptions [Ref 16]).

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## Subjective Effects

**No controlled human studies exist.** All subjective effect data is based on user self-reports, clinical case descriptions, and extrapolation from the NMDA antagonism mechanism.

Published descriptions of effects derived from clinical case reports (Eiden et al. 2018 [Ref 9]), the ACMD review [Ref 18], and class-level pharmacological context (Kang et al. 2017 [Ref 1]; Wallach & Brandt 2018 [Ref 16]):

- **Dissociative/hallucinogenic effects**: documented in all sources as the primary sought-after effects
- **Cognitive impairment**: consistent with NMDA antagonism; memory suppression, disorientation documented
- **Cardiovascular stimulation**: tachycardia and hypertension reported in adverse event cases [Refs 9, 18]
- **Euphoria / cognitive euphoria**: reported by users; consistent with DAT/NET activity
- **Compulsive redosing**: explicitly noted in the French Addictovigilance literature [Ref 9] and ACMD review [Ref 18]; consistent with NMDA tolerance mechanism
- **Duration**: onset 10–30 minutes (oral), total duration 5–7 hours (oral) — seed data consistent with PsychonautWiki and ACMD data; no independent controlled study confirmation

The effect profile is described as comparable to ketamine and PCP given the shared NMDA PCP-site mechanism, with secondary stimulant-like properties from DAT/NET inhibition (Kang et al. 2017 [Ref 1]; Wallach et al. 2016 [Ref 2]).

**No published preclinical behavioral studies for ephenidine specifically.** Diphenidine (the N-deethylated analog/metabolite) demonstrated inhibition of prepulse inhibition in rats with ED₅₀ = 9.5 mg/kg (Wallach et al. 2016 [Ref 2]), providing indirect animal-model evidence of dissociative effects.

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## Safety & Toxicity

### Established Toxic Dose

**The exact toxic dosage for ephenidine is unknown. No LD50 data has been published.** This is stated in the seed data and confirmed by literature review. **FLAG: safety-critical value absent.**

### Clinical Adverse Events (Ephenidine-Specific)

**French Addictovigilance Network** (Eiden et al. 2018 [Ref 9]):
- 4 ephenidine cases reported between 2012 and 2016
- All cases involved polysubstance use (co-ingestion of other NPS)
- No cases classified as "proven" (due to polysubstance confounding); 2 "probable," remainder "possible"
- Complication severity: minor to serious (specific severity breakdown for the 4 ephenidine cases not separable from the aggregate 18-case dataset in the abstract)
- Complications included: psychiatric symptoms, neurological symptoms, cardiovascular problems
- The authors concluded: "The addictive potential of these substances seems highly probable; but further investigations are needed"
- Cases increased from 2013 to 2016, mainly methoxphenidine (ephenidine was a smaller contributor)

### Diarylethylamine Class Mortality (Contextual)

Corkery et al. (2025) [Ref 8] systematic review of diarylethylamine deaths:
- 48 deaths globally involving this compound class
- European deaths: n = 40
- UK deaths: n = 37, occurring 2014–2019
- Characteristics: male 91%, White 95%, mean age 37.2 years (range 19–65), drug use history 72%
- Cause: accidental acute drug toxicity 89%, 92% of causes
- Diphenidine/MXP implicated with other substances (opioids, benzodiazepines, stimulants) in 66% of cases; one-third of deaths involved MXP/diphenidine **alone** — suggesting intrinsic toxicity potential even without polypharmacy
- **Ephenidine is not separately enumerated in the available abstract.** The systematic review covers the class. **FLAG: ephenidine-specific mortality data not confirmed; class-level data only.**

### Clinical Features of Toxicity

From ACMD review [Ref 18] (covers diphenidine, MXP, and ephenidine as a class):
- Acute stimulant and neuropsychiatric toxicity profile
- **Hypertension**
- **Tachycardia**
- **Hallucinations**
- **Confusion**
- **Rhabdomyolysis** (muscle breakdown — clinically significant for renal risk)

### Structural Analog Fatality Reference

A structural analog (methoxphenidine) caused a fatality in a 55-year-old man in a chemsex context (Goncalves et al. 2022 [Ref 21]); postmortem MXP blood concentration: 606 µg/L (femoral). This represents the only published blood concentration data for a lethal diarylethylamine poisoning. No equivalent data exists for ephenidine.

### Dependence Potential

The Eiden et al. (2018) [Ref 9] analysis explicitly states that addictive potential is "highly probable." A case report of methoxphenidine use disorder (Champeau et al. 2017 [Ref 20]) demonstrates the dependence liability of the compound class. Compulsive redosing is documented in multiple sources and is mechanistically consistent with NMDA tolerance development.

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## Harm Reduction

### Testing and Identification

- GC-MS is a standard method for identification; ephenidine and diphenidine can be differentiated by distinct iminium ions (diphenidine: m/z 174) (Wallach et al. 2015 [Ref 17])
- Low-field ¹H NMR (60 MHz) can differentiate ephenidine from related diarylethylamine isomers and regioisomers (Hulme 2018 dissertation; Antonides et al. 2019 [Ref 6])
- Colorimetric/reagent tests may produce false positives for structurally related compounds
- The substance has appeared in drug checking contexts: propylphenidine (the N-propyl analog) was identified at an Australian drug checking service when a sample was presented as a different substance (Algar et al. 2024 [Ref 7]), illustrating the risk of adulteration or mislabeling in the phenidine class

### Contraindications

No published clinical data establishes specific contraindications for ephenidine. From class-level evidence and mechanistic inference:
- **MAO inhibitors**: high-risk combination due to sympathomimetic effects from DAT/NET inhibition; ephedrine/MAOI combinations cause hypertensive crisis by analogous mechanism — **FLAG: no published data for this interaction with ephenidine specifically**
- **Depressants (benzodiazepines, opioids)**: respiratory depression risk; multiple diarylethylamine fatalities involved co-administration of opioids/benzodiazepines [Ref 8]
- **Cardiovascular disease / hypertension**: tachycardia and hypertension documented as toxic effects [Ref 18]
- **Psychosis history**: NMDA antagonists can exacerbate psychosis [mechanistic inference; no ephenidine-specific data]

### Emergency Response

No published emergency management guidelines specific to ephenidine. General dissociative toxicity management applies (airway protection, sedation with benzodiazepines for agitation, monitoring for rhabdomyolysis and renal complications per ACMD clinical features [Ref 18]).

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## Tolerance & Dependence

### Tolerance Development

**Mechanism:** NMDA receptor upregulation and desensitization with repeated dosing (class-level inference). No ephenidine-specific tolerance studies published. The seed data proposes:
- Buildup: "develops with prolonged and repeated use"
- Tolerance half-life: 5 days
- Full reset: 1.5 weeks
- Cross-tolerance: with other dissociatives

**Assessment:** The tolerance framework is plausible given NMDA antagonism mechanism (shared with ketamine, where tolerance development is documented). However, the specific values (5 days half-life, 1.5 weeks reset) are **not confirmed by any published source**. **FLAG: these values are unverified; should be labeled as community-inferred.**

### Compulsive Redosing

Multiple published sources document compulsive redosing with diarylethylamine dissociatives, including ephenidine specifically (Eiden et al. 2018 [Ref 9]; ACMD review [Ref 18]; Corkery et al. 2025 [Ref 8]). This is a mechanistically expected consequence of rapid tolerance development during a session.

### Dependence Liability

A case of methoxphenidine use disorder has been formally documented (Champeau et al. 2017 [Ref 20]) — the first for a diarylethylamine-class dissociative. The French Addictovigilance authors assess addictive potential as "highly probable" (Eiden et al. 2018 [Ref 9]). The seed data categorizes dependence as "moderate" for both physical and psychological, with "moderately addictive with a high potential for abuse" — this is **reasonable by class inference** but **not confirmed by any ephenidine-specific published study**.

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## Interactions

### Published Drug Interaction Data

No published drug interaction studies for ephenidine specifically. All interaction data is by class inference.

**Documented class-level interactions from Corkery et al. (2025) [Ref 8]:**
- 66% of diarylethylamine fatalities involved co-administration with opioids, benzodiazepines, or stimulants
- Opioid co-ingestion: highest risk for respiratory depression
- Stimulant co-ingestion: cardiovascular risk augmentation

**CYP-mediated interaction risk (Wink et al. 2015 [Ref 11]):**
- N-dealkylation involves CYP1A2, CYP2B6, CYP2C19, CYP2D6, and CYP3A4
- Multiple enzyme involvement → **low CYP-mediated drug-drug interaction risk** for the primary metabolic step
- However, potent CYP inhibitors (e.g., fluconazole for CYP2C19; fluvoxamine for CYP1A2) could theoretically impair metabolism and raise plasma levels

**Mechanistic interaction concerns:**
- **CNS depressants (opioids, benzodiazepines, alcohol, GHB)**: additive respiratory and CNS depression
- **MAO inhibitors**: sympathomimetic amplification via NET/DAT inhibition → hypertensive crisis risk
- **Stimulants (amphetamines, cocaine)**: opposing mechanisms but potentially additive cardiovascular stress
- **Serotonergic agents**: sigma receptor affinities (629/722 nM) could theoretically contribute; no evidence of serotonin syndrome risk from this compound alone, but combination with serotonergic drugs should be considered cautiously
- **Other NMDA antagonists (ketamine, PCP, MXE, DXM)**: additive dissociative and toxic effects; combination not advisable

**FLAG: No published pharmacodynamic interaction data for ephenidine. All interaction risk above is by class inference or mechanistic extrapolation.**

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## Legal Status

| Jurisdiction | Status | Instrument/Date |
|---|---|---|
| Sweden | Controlled hazardous substance | 18 August 2015 |
| Canada | Schedule I controlled substance | March 2016 |
| UK | Psychoactive Substances Act (generic ban) | May 2016 |
| UK | Class B, Misuse of Drugs Act | 20 March 2024 (SI 2024/190) |
| France | Narcotic (Annex IV) | Following 2015–2016 adverse event surge |
| Germany | Controlled under narcotics legislation | date unconfirmed |
| Australia | Schedule 9 (Prohibited substance, SUSMP) | October 2024 |
| USA | No specific federal scheduling | Possible coverage under Federal Analog Act or as lefetamine isomer (Sch IV); not confirmed |
| International (UN) | Not separately scheduled; parent compound diphenidine added to Schedule II, UN 1971 Convention | April 2021 (CND 64th session) |

**WHO ECDD status:** Ephenidine has not been independently reviewed by the WHO Expert Committee on Drug Dependence. The 43rd ECDD (2020) reviewed and recommended diphenidine for Schedule II control; fluorolintane, ephenidine, and isophenidine were noted as not yet reviewed [web_retrieved from WHO ECDD materials].

**UK Class B scheduling rationale (ACMD [Ref 18]):** The ACMD recommended scheduling ephenidine alongside diphenidine and methoxphenidine based on similar pharmacological action and toxicity to ketamine, 37 UK deaths in the compound class (2014–2019), and documented addictive potential.

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## Clinical Trials

**No clinical trials have been registered for ephenidine** (ClinicalTrials.gov search: 0 results). No IND filings or clinical development program has been identified. The compound has no therapeutic application under investigation.

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## Community Feedback Analysis

No community feedback was submitted in Part A2 of the brief.

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## Gaps & Flags

### Safety-Critical Values Not Confirmed by Published Sources
1. **⚠️ LD50 / toxic dosage**: Not established. No published data.
2. **⚠️ Tolerance half-life (5 days) and full reset (1.5 weeks)**: Seed data values, not confirmed by any published study. Should be labeled as community-inferred estimates.
3. **⚠️ Dependence severity ("moderate" physical and psychological)**: Plausible by class inference; not supported by ephenidine-specific published data.

### Missing Chemical Data (Now Resolved)
- SMILES, InChIKey, molecular formula, molecular weight, and PubChem CID were absent from seed data — **now confirmed** from PubChem CID 110821.

### Data Absent from Published Literature
- **No human pharmacokinetic studies** (bioavailability, Tmax, elimination half-life, plasma protein binding)
- **No LD50 or minimum toxic dose data**
- **No controlled human dosing studies** (all dose/duration data from user self-reports and ACMD)
- **No published clinical trials**
- **No ephenidine-specific stereochemical pharmacology** (only class analog data from diphenidine available)
- **No specific physical properties** (solubility, logP, boiling point) published in peer-reviewed literature
- **No opioid receptor binding data** (relevant given lefetamine's opioid activity; not measured in Kang et al. 2017)
- **Ephenidine-specific mortality count unknown**: The 2025 Corkery systematic review covers the class; ephenidine-specific death count not available from the abstract

### Reliance on Class Analog Inference
The following data points are extrapolated from diphenidine or class-level data rather than ephenidine-specific research:
- Enantioselective NMDA pharmacology
- CYP drug-drug interaction risk profile
- Dependence severity
- Behavioral effects (PPI data from diphenidine)
- Cross-tolerance with other dissociatives

### Contradictions Between Seed Data and Published Sources
- No significant contradictions identified. Dose ranges in seed data (threshold 30 mg, light 30–70 mg, common 70–100 mg, strong 100–150 mg, heavy 150+ mg) are consistent with ACMD data (typical 70–100 mg) and PsychonautWiki. Duration (onset 10–30 min, total 5–7 hours) is consistent across sources.
- Seed data correctly identifies DAT and NET as secondary pharmacological targets alongside NMDA.

### Unresolved Editorial Questions
1. **Lefetamine isomer legal status in the US**: Whether ephenidine can be prosecuted as a lefetamine analog under the Federal Analog Act remains legally ambiguous and has not been tested in US courts per available evidence.
2. **Ephenidine-specific death count**: The Corkery 2025 systematic review should be obtained in full to determine whether ephenidine deaths are enumerated separately from diphenidine/MXP.
3. **WHO ECDD review**: Ephenidine has not been submitted for international scheduling review; no timeline established.