Methoxphenidine (MXP)
Methoxphenidine (MXP, 2-MeO-diphenidine) is a diarylethylamine dissociative that emerged around 2013 as a legal ketamine substitute. It is an NMDA receptor antagonist producing dissociation, stimulation and, at higher doses, anaesthesia and confusion. Human data are limited to case reports and anecdote, and it has been implicated in several deaths.
01 Overview
MXP belongs to the diphenidine family rather than the arylcyclohexylamines, but shares the core NMDA-antagonist dissociative pharmacology. It became popular as a research chemical when ketamine analogues were scheduled, and is typically taken orally.
Effects are strongly dose-dependent with a slow, sometimes delayed onset that has driven accidental redosing and overdose. Higher doses cause heavy dissociation, ataxia, hypertension, tachycardia, confusion and, in overdose, agitation and cardiovascular strain. Its long duration compounds the redosing hazard.
02 Mechanism
Non-competitive NMDA receptor antagonist; a diarylethylamine that binds the PCP site within the NMDA channel.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Light | 40–70 mg | Oral | Slow onset; wait before considering more. |
| Common | 70–120 mg | Oral | Delayed onset drives accidental redosing. |
| Strong | 120–180 mg | Oral | Heavy dissociation, confusion, cardiovascular strain. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| DissociationDetachment, depersonalisation and 'hole'-like states at high doses. | Anecdotal | ||
| StimulationEnergising, sometimes euphoric effect at lower doses. | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Hypertension and tachycardiaRaised blood pressure and heart rate reported in case reports and intoxications. | Moderate | Common | Observational | |
| Confusion and agitationMarked confusion, disorientation and agitation, sometimes requiring hospital care. | Severe | At higher doses | Observational | |
| Ataxia and loss of coordinationUnsteady gait and impaired motor control with fall risk. | Moderate | Very common | Anecdotal |