MDMA

# Research Output: MDMA

## Chemical Identity

**PubChem CID:** 1615 [confirmed via API]
**Molecular formula:** C₁₁H₁₅NO₂ [Ref 1, PubChem]
**Molecular weight:** 193.24 g/mol (free base); 229.70 g/mol as HCl salt
**IUPAC name:** 1-(1,3-benzodioxol-5-yl)-N-methylpropan-2-amine [PubChem CID 1615]
**InChIKey:** SHXWCVYOXRDMCX-UHFFFAOYSA-N [PubChem CID 1615]
**CAS number:** 42542-10-9 (racemate); 64057-70-1 (S-enantiomer HCl)
**Systematic name:** 3,4-methylenedioxy-N-methylamphetamine (MDMA)

**Seed data discrepancies:** The brief's SMILES, molecular formula, molecular weight, and InChIKey fields were blank. All have now been confirmed via PubChem (CID 1615). PubChem CID should be updated to 1615.

**Physical properties:**
- Free base: colorless oil, insoluble in water [web_retrieved]
- HCl salt: white crystalline powder or crystals; melting point 147–153°C; water-soluble; MW 229.70 g/mol [web_retrieved]
- Solubility (HCl salt): soluble in water and methanol; slightly soluble in acetone; insoluble in diethyl ether [web_retrieved]

**Stereochemistry:** MDMA is marketed and used recreationally as a racemic mixture of S(+)-MDMA and R(-)-MDMA. The two enantiomers have substantially different pharmacological profiles. S(+)-MDMA is more potent at SERT and DAT, producing stronger stimulant and oxytocin-releasing effects and shorter half-life (~4.1 h). R(-)-MDMA is relatively selective for 5-HT₂A receptors, has lower potency at transporters, and has a much longer half-life (~12–14 h) due to differential CYP2D6 metabolism (Straumann et al. 2024 [Ref 28]; Huot et al. 2011 [Ref 7]).

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## Pharmacology

### Mechanism of Action

MDMA is a substrate-type monoamine transporter releaser: it enters presynaptic terminals via the plasma membrane transporters and drives carrier-mediated reverse transport, flooding the synapse with monoamines. This distinguishes MDMA from blockers like cocaine (Green et al. 2003 [Ref 1]).

**Transporter selectivity (release assay EC₅₀ values, Pifl et al. 2005 [Ref 17]):**
- NET (norepinephrine transporter): EC₅₀ = 0.64 µM
- SERT (serotonin transporter): EC₅₀ = 1.12 µM
- DAT (dopamine transporter): EC₅₀ = 3.24 µM

MDMA shows marked serotonin-preferential releasing activity (SERT/DAT ratio ~0.35 when comparing release potencies). This is in contrast to amphetamine, which strongly prefers DAT. The entactogenic/empathogenic character of MDMA relative to classical stimulants is attributed to this serotonin preference (Green et al. 2003 [Ref 1]; de la Torre et al. 2004 [Ref 4]).

**TAAR1 agonism:** MDMA is also a trace amine-associated receptor 1 (TAAR1) agonist, contributing to its monoamine-releasing and stimulant effects (Bunzow et al. 2001 [Ref 44]).

**Enantiomer pharmacology (Huot et al. 2011 [Ref 7]):**
- S(+)-MDMA: potent SERT inhibitor (SERT/DAT ratio ~10:1), drives DA and 5-HT release; responsible for most stimulant and entactogenic effects
- R(-)-MDMA: relatively selective 5-HT₂A receptor activity; contributes to mild perceptual effects; anti-dyskinetic in primate models; less motor-stimulant

**Neuroreceptor substrates of subjective effects** (Liechti & Vollenweider 2001 [Ref 20]; N=44 healthy volunteers):
- Citalopram (SERT blocker) markedly reduced most subjective effects (mood, extraversion, self-confidence) and cardiovascular/adverse effects → confirms 5-HT carrier-mediated release as primary mechanism
- Haloperidol (D₂ antagonist) selectively reduced positive mood/euphoria → confirms partial dopaminergic mediation of euphoria
- Ketanserin (5-HT₂ antagonist) selectively reduced perceptual changes and emotional excitation → 5-HT₂A mediates mild hallucinogen-like effects

**Oxytocin release:** MDMA (1.5 mg/kg oral) increased plasma oxytocin to a mean peak of 83.7 pg/mL at 90–120 min (vs. 18.6 pg/mL placebo) in a double-blind crossover study (Kirkpatrick et al. 2014 [Ref 22]). This mechanism is proposed to underlie prosocial effects, though direct causal evidence remains limited. S-MDMA increases oxytocin more than racemic MDMA or R-MDMA (Straumann et al. 2024 [Ref 28]).

### Pharmacokinetics (Human)

**Oral bioavailability:** High (generally estimated >70%), though precise values from formal bioavailability studies in humans are not well-published at standard therapeutic doses.

**Tmax:** Approximately 1.5–2 hours after oral administration (de la Torre et al. 2004 [Ref 4]).

**Plasma half-life (racemic mixture):**
- S-MDMA component: ~5.1 h
- R-MDMA component: ~11 h
(Straumann et al. 2024 [Ref 28]; these represent the most precise published human half-life values to date)

**Earlier estimates** from human pharmacokinetic studies quoted overall half-life in the range of 7–8 hours (de la Torre et al. 2004 [Ref 4]; Cami et al. 2000 [Ref 14]).

**Metabolism:** Two main hepatic pathways (de la Torre et al. 2004 [Ref 4]):
1. **O-demethylenation** (primary): CYP2D6-mediated conversion to 3,4-dihydroxymethamphetamine (HHMA), then O-methylation by COMT to 4-hydroxy-3-methoxymethamphetamine (HMMA), followed by glucuronide/sulfate conjugation. This is the major pathway for elimination.
2. **N-dealkylation**: Produces 3,4-methylenedioxyamphetamine (MDA), which is also pharmacologically active, followed by deamination and oxidation.

**CYP2D6 mechanism-based inhibition:** MDMA forms an enzyme-metabolite complex that irreversibly inhibits CYP2D6. Critically, this renders all individuals phenotypically "poor metabolizers" after as few as 2 consecutive doses, regardless of genotype. This limits the clinical impact of CYP2D6 polymorphism for acute toxicity but raises interaction concerns with CYP2D6-metabolized drugs (Segura et al. 2005 [Ref 6]; Yubero-Lahoz et al. 2011 [Ref 5]).

**Sex differences:** CYP2D6 inhibition recovery half-life differs between males and females; females show somewhat different pharmacokinetic profiles (Yubero-Lahoz et al. 2011 [Ref 5]).

**Protein binding:** Low (<20% for amphetamine-type stimulants); MDMA distributes widely (de la Torre review 2004 [Ref 4]).

**Urinary excretion:** A portion of MDMA is excreted unchanged. Both hepatic and renal clearance contribute to elimination.

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## History

**1912 — Synthesis at Merck:**
MDMA was first synthesized by Anton Köllisch at the German pharmaceutical company Merck in 1912. At that time it was recorded as "Methylsafrylamin" in internal lab journals, not by its modern name. The substance was not developed as an appetite suppressant or for recreational use — a widely repeated myth. Merck's patent was filed to protect an alternative synthesis route for **hydrastinine**, a hemostatic agent, in order to circumvent a Bayer patent. MDMA was merely an unimportant intermediate in this process. No meaningful pharmacological testing occurred until 1927, and those tests were halted for economic reasons. In the 1950s, primitive toxicological studies were conducted but MDMA was not tested in humans at that time (Freudenmann et al. 2006 [Ref 18]; Bernschneider-Reif et al. 2006 [Ref 19]).

**1953–1954 — US Army interest:**
Limited evidence suggests the US Army investigated MDMA as part of a series of psychoactive drug studies, though declassified records are sparse (noted in historical accounts; not confirmed via published peer-reviewed source — flagged as unverifiable).

**1976 — Shulgin's rediscovery:**
Alexander T. Shulgin, a chemist who was introduced to MDMA through associates at San Francisco State University, developed a new synthesis method and self-experimented with the compound. He introduced it to Leo Zeff, a psychologist from Oakland, California. Shulgin published the first systematic human pharmacological description of MDMA (though his formal paper came later). Zeff went on to introduce MDMA to a network of therapists (Benzenhöfer & Passie 2010 [Ref 33]).

**Late 1970s–1985 — Psychotherapeutic use:**
Hundreds of psychotherapists, particularly on the US West Coast, used MDMA as an adjunct to psychotherapy under the name "Adam" (for its reputed capacity to restore a sense of primal innocence). Use spread to recreational contexts in the early 1980s under the name "Ecstasy." MDMA was used legally in Switzerland for psychotherapy from 1988–1993 (Oehen et al. 2013 [Ref 25]).

**1985 — DEA scheduling:**
In July 1985, the DEA invoked emergency scheduling authority to place MDMA temporarily into Schedule I. An Administrative Law Judge recommended against permanent Schedule I placement, arguing MDMA had accepted medical use. The DEA administrator overruled this recommendation, and MDMA was permanently placed in Schedule I in March 1986 [Ref 29].

**1988 — Neurotoxicity evidence emerges:**
O'Hearn et al. (1988) published immunocytochemical evidence that MDA and MDMA cause selective ablation of serotonergic axon terminals in rat forebrain, establishing the neurobiological basis for concerns about neurotoxicity that persist to the present day [Ref 3].

**2010s — Clinical renaissance:**
MAPS-sponsored Phase 2 clinical trials began demonstrating safety and efficacy of MDMA-assisted psychotherapy for PTSD (Mithoefer et al. 2011 [Ref 32]; Oehen et al. 2013 [Ref 25]).

**2017 — FDA Breakthrough Therapy Designation:**
The FDA granted Breakthrough Therapy Designation to MDMA-assisted therapy for PTSD based on Phase 2 results (Yazar-Klosinski & Mithoefer 2017 [Ref 34]).

**2021–2023 — Phase 3 Trials:**
Phase 3 MAPP1 (Mitchell et al. 2021 [Ref 2], NCT03537014) and Phase 3 MAPP2 (Mitchell et al. 2023 [Ref 31], NCT04077437) both demonstrated significant PTSD symptom reduction. Combined effect sizes (d=0.91 and d=0.70 respectively) were large.

**July 2023 — Australian rescheduling:**
Australia's Therapeutic Goods Administration rescheduled MDMA to Schedule 8 (controlled drug), permitting prescribing for PTSD by authorized psychiatrists under the Authorised Prescriber scheme — the first country globally to take this step [Ref 41].

**August 2024 — FDA rejection:**
The US FDA voted against approving MDMA-assisted therapy for PTSD. Concerns cited included: failure of blinding integrity, absence of certain safety assessments (QT prolongation, abuse liability), and allegations of potential research misconduct (Singh 2025 [Ref 11]). The Mithoefer et al. 2019 pooled Phase 2 analysis paper was also retracted [Ref 30].

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## Subjective Effects

The following effects are documented in published controlled human studies, cross-referenced with the brief's effects taxonomy.

**Controlled study data (Cami et al. 2000 [Ref 14], N=8 healthy males, 75mg and 125mg oral):**
- Marked euphoria and well-being (ARCI MBG and A scales elevated)
- Increased stimulation, energy, "high" feeling
- Mild psychomotor impairment (DSST: slight decrease in responses at 125mg)
- Mild esophoria (eye deviation) at 125mg
- Enhanced sedation-related and mild dysphoria-related effects (paradoxically, PCAG scale elevation)
- Mild changes in body perception; no hallucinations or psychoses

**From Liechti & Vollenweider 2001 [Ref 20] (1.5 mg/kg oral; citalopram blocks most effects):**
- Positive mood, increased extraversion and self-confidence
- Mild hallucinogen-like perceptual changes (blocked by ketanserin)
- Cardiovascular stimulation (blood pressure, heart rate elevations)

**From Schmid et al. 2014 [Ref 39] (75mg; N=30 healthy subjects):**
- Enhanced emotional empathy (increased positive emotional empathy in MET)
- Tended to reduce recognition of sad facial expressions
- Subjective "empathogenic" effects: drug liking, closeness to others, openness, trust
- Increased plasma oxytocin and prolactin at 75mg

**From Straumann et al. 2024 [Ref 28] (125mg racemic vs. S-MDMA and R-MDMA; N=24):**
- S-MDMA 125mg: greater stimulation, "drug high," happy, open, higher blood pressure than racemic MDMA
- R-MDMA 250mg: substantially weaker effects overall; did not produce more psychedelic-like effects than S-MDMA

**Duration (from published controlled study timing and brief's existing data):**
- Onset: 30–45 minutes (oral)
- Come-up: 15–30 minutes (oral)
- Peak: 1.5–2.5 hours (oral)
- Total duration: 3–6 hours (oral)
- Aftereffects: 12–48 hours

These values are consistent with clinical trial session data where MDMA sessions are scheduled for 8 hours and effects typically resolve within that window (Mithoefer et al. 2011 [Ref 32]; Oehen et al. 2013 [Ref 25]).

**Memory effects (Doss et al. 2018 [Ref 28 — see note]):** MDMA (1 mg/kg) impaired both encoding and retrieval of emotional episodic memory, particularly reducing recollection of negative and positive emotional events. This may be relevant to its therapeutic mechanism in PTSD (PMID 28825422).

**Social cognition (Borissova et al. 2021 [Ref 13]):** MDMA acutely increased trust and cooperative behavior in double-blind experiment; enhanced prosocial motivation.

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## Safety & Toxicity

### Acute Toxicity

**LD50 in animals:** Animal LD50 data show significant variability by species, strain, sex, ambient temperature, and route. In Sprague-Dawley rats, oral LD50 is approximately 97 mg/kg with substantial sex differences (males ~2.4-fold more sensitive than females, attributed to CYP1A2-mediated production of the neurotoxic metabolite MDA) [web_retrieved; no peer-reviewed PubMed primary source with specific rat LD50 found — flagged]. In mice, LD50 varies considerably with temperature. **No human LD50 has been established.** The brief correctly notes "exact toxic dosage is unknown." This is confirmed — no published study has established a human toxic threshold or LD50.

**Therapeutic index:** Not established in humans. In clinical trials (doses up to 180mg over a session with supplements), MDMA has been administered to >1,133 individuals without drug-related serious adverse events (Danforth et al. 2016 [Ref 24]).

### Acute Adverse Events

**Cardiovascular:** Moderate increases in blood pressure and heart rate; vasoconstriction (including in coronary vasculature); effects are substantially greater in hyperthermia conditions (Fonseca et al. 2017, PMID 28084566). The Mitchell et al. 2021 Phase 3 trial [Ref 2] found no QT prolongation.

**Hyperthermia:** A key mechanism of severe MDMA toxicity. MDMA impairs thermoregulation through multiple mechanisms (5-HT-mediated thermogenesis, vasoconstriction limiting heat dissipation, physical exertion in hot environments). Temperature dysregulation is enhanced at high ambient temperatures and can be fatal in rodents, primates, and humans (Green et al. 2003 [Ref 1]). The combination of MDMA, physical exertion, and hot/crowded environments (nightclubs, raves) is the most common context for fatal hyperthermia cases (Parrott 2006 [Ref 35]).

**Hyponatremia:** MDMA causes syndrome of inappropriate antidiuretic hormone secretion (SIADH), and users also often drink excess water due to perceived dehydration. The combination produces dilutional hyponatremia and risk of cerebral edema (Traub et al. 2002 [Ref 15]; Khalifa & Abdulmajeed 2025 [Ref 16]). A 19-year-old female presented with serum Na⁺ of 121 mmol/L and cerebral edema after MDMA use; treated with hypertonic saline and fluid restriction (Traub 2002 [Ref 15]).

**Hepatotoxicity:** MDMA-induced liver toxicity can occur dose-independently after a symptom-free period of days to weeks post-ingestion. Mechanisms include thermal injury, direct metabolite toxicity, and possible genetic susceptibility. Cases of acute fulminant hepatic failure requiring liver transplantation have been reported in young users (Lange-Brock et al. 2002 [Ref 42]).

**Rhabdomyolysis and DIC:** Reported in severe MDMA toxicity cases (Rogers et al. 2009 [Ref 37]).

**Serotonin syndrome:** Characterized by hyperthermia, muscle rigidity, hyperreflexia, and autonomic instability. Can be triggered by MDMA alone at high doses or in combination with serotonergic drugs. Constitutes a medical emergency (de la Torre et al. 2004 [Ref 4]; Rogers et al. 2009 [Ref 37]).

**WHO VigiBase data (Syed et al. 2026 [Ref 27]):** MDMA had the largest number of adverse event reports of any psychedelic substance (n=1,573) in the global pharmacovigilance database. Most AEs were psychiatric in nature. Overdose constituted 1.1–1.7% of total AEs. MDMA was associated with significantly higher odds of reported substance use disorder and dependence compared to acetaminophen control (SUD ROR=129.9, 95% CI 78.4–215.5).

### Long-Term Neuropsychological Effects

**Serotonergic neurotoxicity (animal data):** O'Hearn et al. (1988 [Ref 3]) demonstrated selective ablation of serotonergic axon terminals throughout the rat forebrain after repeated high-dose MDMA, with catecholaminergic neurons spared. In primates, 5-HT depletion persists for years. In mice, MDMA produces selective dopaminergic neurotoxicity instead (Green et al. 2003 [Ref 1]).

**Mechanism:** Free radical formation from MDMA metabolites (catechol metabolites, quinones). Temperature-dependent: neurotoxicity is substantially reduced when hyperthermia is prevented. SERT is required for full expression of toxicity (Lizarraga et al. 2014, PMID 24595820).

**Human evidence:** Evidence for neurotoxicity in humans remains contested but growing. Heavy MDMA users show:
- Reduced SERT availability in multiple brain regions on neuroimaging; some evidence for recovery with prolonged abstinence (van de Blaak & Dumont 2022 [Ref 8])
- Reduced hippocampal grey matter volume correlated with recent MDMA use intensity (hair concentrations), and verbal memory impairment; structural changes correlated with 5-HT1A, 5-HT2A, and 5-HT4 receptor density patterns (Coray et al. 2026 [Ref 38], N=122)
- Meta-analysis: overall executive function deficit (SMD = −0.18; 95% CI −0.26 to −0.11); significant deficits in updating, switching, and access to long-term memory (Roberts et al. 2016 [Ref 9])
- Baumann et al. (2007 [Ref 36]) debate whether these reflect true neuronal damage vs. adaptive 5-HT downregulation

**Confounders:** Heavy ecstasy users typically consume multiple drugs; premorbid differences cannot be excluded. Studies controlling for polydrug use (Halpern et al. 2011, PMID 21205042) suggest persistent but modest neurocognitive deficits in relatively pure MDMA users.

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## Harm Reduction

**Temperature management:** The combination of MDMA, physical exertion, and hot environments is the most common proximate cause of fatal hyperthermia. Users should avoid strenuous physical activity, take regular breaks, and access cool environments. Ambient temperature is strongly correlated with neurotoxic outcomes (Parrott 2006 [Ref 35]; Green et al. 2003 [Ref 1]).

**Hydration:** Users should drink approximately 500 mL/hour of water if dancing, but NOT over-hydrate. Excessive water intake, combined with MDMA-induced SIADH, is a leading cause of hyponatremia-related deaths (Traub et al. 2002 [Ref 15]). Electrolyte drinks are preferable to plain water.

**Drug testing:** MDMA tablets frequently contain adulterants. Testing with reagent kits (Marquis, Simon's, etc.) and drug checking services (where legal) reduces risk of consuming misidentified substances. No published primary source retrieved specifically on harm-reduction testing protocols — flagged.

**Dose titration and interval:** Given the nonlinear dose-response relationship and risk of acute tolerance/redosing within a session, lower initial doses and avoiding redosing reduce risk. The database brief notes "compulsive redosing urge" as a recognized effect.

**Contraindications (from literature):**
- MAOIs (including phenelzine, tranylcypromine, selegiline, moclobemide, reversible): serotonin syndrome and fatalities documented (Rached et al. 2026 [Ref 26])
- Concurrent stimulants: additive cardiovascular toxicity
- Tramadol and DXM: serotonergic toxicity risk (Rached et al. 2026 [Ref 26])
- Known cardiovascular disease: exacerbated hemodynamic effects, particularly in hyperthermia
- Hepatic disease: reduced detoxification capacity
- Pre-existing psychiatric illness: limited safety data; particularly relevant for individuals with psychosis spectrum conditions

**Clinical contraindications identified in Phase 3 trials (Mitchell et al. 2021 [Ref 2]):** Participants underwent psychiatric medication washout before MDMA sessions. Trial included individuals with common comorbidities (dissociation, depression, AUD, childhood trauma) without safety concerns.

**Emergency response:** Suspected MDMA serotonin syndrome/hyperthermia requires prompt cooling (ice packs to axillae/groin, cool IV fluids, cooling blankets), benzodiazepines for seizures and agitation, cyproheptadine (5-HT antagonist) where available, and airway management. Hyponatremic cerebral edema requires hypertonic saline and fluid restriction; ICP monitoring in severe cases (Khalifa & Abdulmajeed 2025 [Ref 16]).

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## Tolerance & Dependence

**Acute pharmacodynamic tolerance:** Documented within a single session — the subjective effects of a second dose are attenuated compared to the first (Hysek et al. 2014 [Ref 40]). This contributes to the clinical protocol of supplemental dosing at ~50% of the initial dose (rather than full re-dosing).

**Interuse tolerance:** MDMA produces rapid depletion of presynaptic 5-HT stores. Repeated use within short intervals produces diminishing subjective effects. Full recovery is estimated at several weeks to months based on animal and human SERT data (van de Blaak & Dumont 2022 [Ref 8]). The brief states: tolerance half-life 1 month, full reset 2.5 months — these align qualitatively with published SERT recovery timeframe data.

**Cross-tolerances:** Dopaminergic, serotonergic, stimulant cross-tolerances are biologically plausible given the mechanism and are consistent with the brief's listing.

**Dependence and addiction liability:**
- MDMA produces conditioned place preference in mice at 10 mg/kg (Robledo et al. 2004, PMID 14758467); lower doses (0.3–3.3 mg/kg) did not produce CPP.
- Physical withdrawal was not clearly characterized in animal models — no classical somatic signs on abrupt cessation. Serotonergic antagonists (metergoline, ritanserin) precipitated some signs (paw tremor) in chronically treated mice, suggesting serotonergic dependence component.
- Human epidemiology: higher odds of reported substance use disorder and dependence vs. controls in WHO VigiBase data (Syed et al. 2026 [Ref 27])
- Cognitive impairment during MDMA withdrawal may involve hippocampal arachidonic acid cascade (Nawata et al. 2024, PMID 38430788)
- The brief's characterization of "moderate physical dependence, moderate psychological dependence, moderately addictive with high potential for abuse" is broadly consistent with evidence, though "high potential for abuse" is not consistently supported in the controlled clinical literature where abuse potential was not observed in trial participants (Mitchell et al. 2021 [Ref 2]).

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## Interactions

### Lethal Interactions

**MAO inhibitors (MAOIs):** Combining MDMA with MAOIs is potentially fatal. MAOIs block the enzymatic degradation of serotonin; MDMA simultaneously drives massive serotonin release. The resulting serotonin toxicity can include hyperthermia >41°C, muscle rigidity, rhabdomyolysis, and multi-organ failure. Both irreversible (phenelzine, tranylcypromine) and reversible (moclobemide) MAOIs are implicated. Fatalities documented (Rached et al. 2026 [Ref 26]).

**Tramadol:** Tramadol has both opioid and serotonergic reuptake inhibitor properties; combined with MDMA's massive serotonin release, serotonin syndrome with fatal outcomes has been reported (Rached et al. 2026 [Ref 26]; brief lists as "lethal").

**Dextromethorphan (DXM):** DXM is a SERT inhibitor and, at high doses, a dissociative. Combined with MDMA, serotonin syndrome with fatal outcomes can occur (brief lists as "lethal"). At high DXM doses, the interaction is analogous to an MAOI combination.

**αMT (alpha-methyltryptamine):** Listed as lethal in brief; αMT has both monoamine-releasing and MAOI properties, making the combination with MDMA similar to an MAOI interaction.

**Methylnaphthidate (MNMP):** Listed as lethal in brief. Primarily a catecholamine reuptake inhibitor; the lethal designation likely relates to combined cardiovascular and serotonergic toxicity. No published primary source found — flagged.

**2-Aminoindane (2-AI):** Listed as lethal in brief. 2-AI has NET-preferring activity and may cause serotonergic crisis in combination; no published primary case report found — flagged.

### Dangerous Interactions (Serotonergic/Cardiovascular)

**SSRIs and SNRIs:** SERT blockers attenuate MDMA's primary mechanism (confirmed: citalopram significantly reduces MDMA's effects; Liechti & Vollenweider 2000 [Ref 21]). However, sudden discontinuation of an SSRI followed by MDMA use, or combining MDMA with an SNRI at high doses, may still produce serotonergic adverse effects. The interaction is complex and dose-dependent.

**Stimulants (amphetamines, cocaine, cathinones, methylphenidate):** Additive cardiovascular toxicity (blood pressure, heart rate, hyperthermia risk). Methylphenidate co-administration with MDMA significantly increased hemodynamic adverse effects without enhancing psychoactive effects (Hysek et al. 2014 [Ref 40]).

**Lithium:** Listed as "dangerous" in the brief. The proposed mechanism is lowering of the seizure threshold; lithium is known to lower seizure threshold independently, and MDMA reduces the threshold further. Additionally, lithium toxicity can be precipitated by fluid/electrolyte disturbances (such as MDMA-induced hyponatremia). No specific published clinical case series found for MDMA + lithium — flagged as requiring editorial verification.

**Other serotonergic substances (5-APB, 6-APB, MDAI, MDA, MDEA, methylone, mephedrone, etc.):** Additive serotonergic toxicity through shared mechanism. Combinations of entactogens are considered dangerous.

### Pharmacokinetic Interactions

MDMA's mechanism-based CYP2D6 inhibition means that any drug metabolized by CYP2D6 taken within ~2 days of MDMA will have substantially elevated plasma concentrations (Segura et al. 2005 [Ref 6]; Yubero-Lahoz et al. 2011 [Ref 5]). This includes many antidepressants, antipsychotics, opioids, and beta-blockers.

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## Legal Status

**United States:** DEA Schedule I under the Controlled Substances Act — placed temporarily July 1985 (emergency scheduling) and permanently in March 1986 [Ref 29]. Despite FDA Breakthrough Therapy Designation granted 2017 [Ref 34], a New Drug Application for MDMA-assisted therapy was rejected by the FDA in August 2024 (Singh 2025 [Ref 11]). As of April 2026, MDMA remains Schedule I with no approved medical use in the US.

**United Kingdom:** Class A controlled substance under the Misuse of Drugs Act 1971. Possession carries up to 7 years imprisonment; supply up to life imprisonment.

**Australia:** Rescheduled from Schedule 9 (prohibited) to **Schedule 8** (controlled drug) effective **1 July 2023** by the Therapeutic Goods Administration. Prescribing permitted by authorized psychiatrists for PTSD treatment only under the TGA Authorised Prescriber scheme [Ref 41]. First country globally to legally permit medical use of MDMA.

**European Union:** Controlled under national law in all EU member states; international scheduling under the UN Convention on Psychotropic Substances (Schedule I). Germany, Netherlands, and others are developing frameworks for research use.

**Canada:** Schedule III under the Controlled Drugs and Substances Act. However, Health Canada has granted Section 56 exemptions for therapeutic use in some clinical contexts (not yet widely available).

**International:** MDMA is listed in Schedule I of the United Nations Convention on Psychotropic Substances (1971), established through WHO and DEA advocacy.

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## Clinical Trials

**Completed Phase 3 Trials:**

| NCT | Title | Status | Reference |
|---|---|---|---|
| NCT03537014 | MAPP1: Phase 3 MDMA-AT for PTSD (N=90) | Completed | Mitchell et al. 2021 [Ref 2] |
| NCT04077437 | MAPP2: Phase 3 MDMA-AT for PTSD (N=104) | Completed | Mitchell et al. 2023 [Ref 31] |
| NCT05979844 | Phase 3 MDMA-AT + Brief CBCT for PTSD | Completed | — |

**Key Phase 2 Trials:**

| NCT | Title | Status | Notes |
|---|---|---|---|
| NCT00090064 (historical) | First MAPS Phase 2 PTSD trial | Completed | Mithoefer et al. 2011 [Ref 32] |
| NCT04264026 | MDMA-AT for Veterans, Combat PTSD | Completed | VA Loma Linda |
| NCT01211405 | Dose-comparison 3 doses + therapy, Veterans | Completed | Lykos Therapeutics |
| NCT01458327 | Additional MDMA-AT after relapse | Completed | Lykos Therapeutics |

**Active/Recruiting Trials of Note:**

| NCT | Title | Phase | Condition | Sponsor |
|---|---|---|---|---|
| NCT06905652 | R-MDMA vs S-MDMA vs racemic in healthy subjects | Phase 1 | Healthy | U Basel |
| NCT06989957 | Psilocybin + MDMA for PTSD | Phase 1 | PTSD | Johns Hopkins |
| NCT07301632 | MDMA for chronic neuropathic pain (EASE trial) | Phase 2 | Chronic pain | Unity Health Toronto |
| NCT05584826 | MDMA-AT for Adjustment Disorder in cancer patients | Phase 2 | Cancer/AD | Sunstone Medical |
| NCT05709353 | MDMA-AT + Prolonged Exposure for PTSD + AUD | Phase 2 | PTSD + AUD | U Sydney |
| NCT07118839 | MDMA-AT for Veterans with PTSD + AUD | Phase 2 | PTSD + AUD | VA |

**Meta-analytic evidence (Fares-Otero et al. 2026 [Ref 10]):** 14 RCTs identified; 8 trials in quantitative synthesis. MDMA-AT associated with significant PTSD symptom reduction (SMD = −1.19; 95% CI −1.95 to −0.42; I² = 68.8%) and functional improvement. However, certainty of evidence rated **very low** per GRADE due to high risk of bias in outcome measurement and heterogeneity. Active controls absent in most studies, compromising blinding integrity.

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## Community Feedback Analysis

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

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## Gaps & Flags

### Safety-Critical Values Not Confirmed by Published Sources

1. **Human LD50 / human toxic threshold:** Not established in published literature. Brief correctly notes "exact toxic dosage is unknown." No correction needed, but generation agent should not claim any specific lethal human dose.

2. **Methylnaphthidate (MNMP) + MDMA — lethal interaction:** Listed as lethal in brief; no published primary clinical source found. Flagged for editorial review.

3. **2-Aminoindane + MDMA — lethal interaction:** Listed as lethal in brief; mechanism is plausible (NET-preferring plus MDMA serotonergic flooding) but no published case report retrieved. Flagged for editorial review.

4. **Lithium + MDMA — "dangerous":** Mechanistically plausible (seizure threshold lowering; electrolyte disturbances from hyponatremia affecting lithium levels), but no published primary clinical case series specifically for this combination was found. Flagged.

5. **GBL/GHB + MDMA — "unknown" in brief:** The interaction risk is real (CNS depression + stimulation; respiratory depression risk; blackout risk) but limited published data specific to MDMA+GHB/GBL found. Brief's "unknown" designation may be appropriate but should be noted.

### Data Gaps

6. **IUPAC name and SMILES not in the brief:** These should be populated. Confirmed via PubChem — see Chemical Identity section above.

7. **PubChem CID not in brief (field blank):** CID = 1615 confirmed.

8. **Human bioavailability data:** Formal bioavailability studies (iv vs. oral comparison) are not well-published for MDMA in humans. General ATS class estimate of >70% used; this should not be stated as MDMA-specific in the article.

9. **Oral dose LD50 in rats:** Multiple sources cite ~97 mg/kg but peer-reviewed primary source with specific value was not retrieved via PubMed API. Used web-retrieved information (flagged as web_retrieved, not api_verified).

10. **Retracted paper note:** Mithoefer et al. 2019 (PMID 31065731) — pooled Phase 2 analysis paper — is listed as RETRACTED in OpenAlex. The generation agent should not cite this paper as a primary source. The data from the individual Phase 2 trials (which are not retracted) remain usable.

11. **Harm reduction testing protocols:** No primary published protocol found via literature search. Reagent testing recommendations are widely disseminated by harm-reduction organizations (DanceSafe, The Loop) but no peer-reviewed primary source was retrieved. Generation agent should source this from grey literature or label as expert consensus.

12. **Dose range — "Dose sensitivity" field blank in brief:** Clinical studies confirm: 75mg (low/common), 125mg (strong therapeutic dose in all Phase 2/3 trials), 150mg+ (heavy). Seed data dose ranges (Threshold: 20mg; Light: 20–80mg; Common: 80–120mg; Strong: 120–150mg; Heavy: 150+mg) are broadly consistent with published controlled study doses and community consensus. No direct flag needed.

13. **Duration data:** Seed data aftereffects of "12–48 hours" are plausible but no controlled study specifically measuring 48-hour outcomes found. Clinical trial follow-ups are typically at 3 days or later. Conservative flagging: aftereffects duration is based on community consensus / anecdotal reporting, not controlled study measurement.

14. **Australia legal status update:** Brief should be updated to note Australia has approved MDMA for PTSD treatment since July 2023 [Ref 41].

15. **FDA 2024 rejection:** Major regulatory development not in brief — generation agent should include this in legal status / clinical context.