4-AcO-DMT
4-acetoxy-N,N-dimethyltryptamine
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4-AcO-DMT (O-acetylpsilocin) — also known as psilacetin — is a synthetic psychedelic of the tryptamine class. It is the acetate ester of psilocin, the active compound in psilocybin mushrooms. It activates serotonin receptors in the brain, producing the visual and cognitive shifts of classical psychedelics.[1][2]
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Hofmann and Troxler synthesized it at Sandoz in 1963, patenting it as a psilocin derivative but never testing its effects.[3] Shulgin called it pharmacologically interchangeable with psilocybin in 1997,[4] and Nichols proposed it as a practical research substitute two years later.[5] It has since circulated through unregulated markets and is the most commonly encountered novel tryptamine in European drug monitoring.
Subjective effects include geometric visual patterns, brightened colors, emotional deepening, introspection enhancement, and ego dissolution at high doses. The experience is warm and body-centered — widely described as indistinguishable from psilocybin mushrooms,[4] and less stimulating than LSD. Nausea, anxiety escalation, thought loops, and confusion are common unwanted effects.
4-AcO-DMT produces no physical dependence, and a single dose causes rapid tolerance that makes compulsive use unlikely.[6] The primary danger is psychological — high doses can produce panic, paranoia, and identity disruption, and combining it with serotonin-raising drugs risks a dangerous overactivation of the serotonin system. No human clinical studies exist; understanding rests on animal pharmacology, lab metabolism studies, and computational modeling.[7]
History[edit]
Discovery
Albert Hofmann and Franz Troxler first synthesized 4-AcO-DMT at Sandoz Pharmaceuticals in Basel, Switzerland in 1963.[3] It appeared in a patent covering psilocin derivatives — a chemical survey, not a pharmacological investigation. The compound was never tested for psychoactivity and received no scientific attention for over thirty years.
Academic Recognition
Alexander Shulgin revived interest in TiHKAL (1997), describing 4-AcO-DMT as "completely interchangeable" with psilocybin in pharmacological effect.[4] David Nichols and Stephen Frescas followed with the first peer-reviewed paper proposing it as a practical substitute for psilocybin in research — simpler to prepare and not yet scheduled.[5]
Market Emergence and Modern Research
4-AcO-DMT appeared on research chemical markets in the early 2000s, initially noted among psychedelic enthusiasts,[8] and was documented as a designer drug in Europe by 2009.[9] Subsequent studies confirmed its metabolism,[2] prodrug behavior,[10] receptor binding,[11] and toxicity profile.[7] No clinical trials have been conducted as of April 2026.
The name psilacetin — a portmanteau of psilocin and acetyl — reflects its identity as psilocin's acetate ester. Among users it is sometimes called "synthetic shrooms," though this label obscures the differences between a pure compound and a complex fungal preparation.
Chemistry[edit]
Structural Class
4-AcO-DMT belongs to the substituted tryptamine family (molecular formula C₁₄H₁₈N₂O₂). It is the acetate ester of psilocin — a structural relationship that means enzymes break it down to psilocin, the same active compound found in psilocybin mushrooms.[2][10]
The N,N-dimethyl group on its side chain is essential for psychedelic activity,[1] and the acetate group breaks down readily under basic conditions, which affects forensic identification.[12]
Pharmacology[edit]
Mechanism of Action
4-AcO-DMT activates serotonin receptors to produce its psychedelic effects through two overlapping routes.[13][14] In the body, enzymes break it down to psilocin,[2][10] which drives most of the response. It also activates those receptors directly in its intact form, producing psychedelic-type responses at potencies comparable to psilocin itself.[1]
At higher doses, a second type of serotonin receptor becomes active and introduces sedation — partially dampening the psychedelic stimulation.[11]
Pharmacokinetics
No human pharmacokinetic data for 4-AcO-DMT have been published. In lab studies, the compound converts primarily to psilocin;[2] in mice, this yields about 70% of the psilocin levels seen with an equivalent psilocybin dose.[10] An enzyme called MAO-A handles roughly 80% of psilocin's breakdown,[15] with the active compound lasting 1.5–4 hours based on psilocybin studies.[16][17]
Neuroscience[edit]
Where It Acts
No brain imaging data for 4-AcO-DMT have been published. Based on its shared active metabolite, it is expected to engage the same cortical and emotional circuits studied in psilocybin neuroimaging research. In rats, it reduces fear responses through serotonin-sensitive neurons in the prefrontal cortex,[18] and in reward studies it produces sustained positive states without the compulsive rebound effect of addictive substances.[6]
Why It Matters
The leading theory holds that psychedelics loosen the brain's built-in mental filters, allowing sensory input more influence on conscious experience.citation needed Under this framework, the effects — brightened perception, fluid thinking, emotional swings, ego dissolution — reflect a temporary shift in how the brain weighs what is happening against what it expects.
Psilocin also stimulates growth of new neural connections through chemical signaling in the brain. Whether 4-AcO-DMT shares this plasticity effect at relevant doses has not been tested directly, though the shared active metabolite makes it likely.citation needed
Whether the roughly 30% lower psilocin exposure from 4-AcO-DMT compared to psilocybin[10] produces meaningful differences in therapeutic outcomes has not been studied. The compound's direct receptor activity before converting to psilocin could produce a distinct neural activation pattern — but this remains untested. The rat prefrontal cortex findings[18] await validation in human neuroimaging.
Subjective Effects[edit]
The 4-AcO-DMT experience is warm, body-centered, and introspective — sustained and immersive rather than sharp or stimulating. At low doses, colors soften and mood lifts. At higher doses, thinking loosens and becomes fluid, emotions deepen, and a sense of being inside the experience displaces ordinary self-awareness.
Most users describe it as indistinguishable from psilocybin mushrooms[4] — the same warmth, body-heaviness, and emotional depth. Compared to LSD, it is shorter, less stimulating, and more emotionally saturated, with a heavier physical quality characteristic of the tryptamine family.
Effect Grid
At common doses (15–25 mg oral), the full psychedelic experience unfolds. Visual effects become pronounced — geometric patterning overlaying surfaces, colour shifting and enhancement, drifting and morphing of objects and textures, and closed-eye visuals with kaleidoscopic imagery. Time distortion is significant; minutes may feel stretched or compressed. Thought connectivity increases, producing novel associations and conceptual linkages. Emotional amplification is marked — responses to music, nature, and interpersonal interaction can feel deeply meaningful.
Physically, nausea during the come-up is common and may lead to vomiting in some individuals. Body load is noticeable as diffuse heaviness or waves of physical sensation. Pupil dilation is prominent. Temperature dysregulation — alternating sensations of warmth and cold — is typical.
Functional impairment is substantial. Sleep is not possible for the duration of effects (4–7 h). Activities requiring coordination, concentration, or social composure are significantly impaired.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Visual drifting · Color alteration · Visual breathing · Environmental patterning · Auditory enhancement · Tracers · Symmetrical texture repetition · Perspective distortion · Visual morphing · Brightness alteration · Touch enhancement · Visual haze / noise · After-images · Depth perception distortion · Visual diffraction · Visual melting · Light sensitivity · Sound sensitivity · Spatial disorientation · Proprioceptive distortion · Peripheral vision distortion · Auditory distortion · Synesthesia · Vestibular distortion · Visual magnification · Auditory misinterpretation · Dreaming enhancement · Peripheral misidentification · Visual acuity enhancement · Visual acuity suppression · Taste enhancement · Olfactory enhancement · Internal hallucinations · Object transformations · External hallucinations · Visual recursion · Auditory hallucinations · Environmental orbism / cubism · Object activation · Visual scenery slicing · Perspective hallucinations · Olfactory hallucination
Auditory enhancement · Tracers · Symmetrical texture repetition · Perspective distortion · Visual morphing · Brightness alteration · Touch enhancement · Visual haze / noise · After-images · Depth perception distortion · Visual diffraction · Visual melting · Light sensitivity · Sound sensitivity · Spatial disorientation · Proprioceptive distortion · Peripheral vision distortion · Auditory distortion · Synesthesia · Vestibular distortion · Visual magnification · Auditory misinterpretation · Dreaming enhancement · Peripheral misidentification · Visual acuity enhancement · Visual acuity suppression · Taste enhancement · Olfactory enhancement · Internal hallucinations · Object transformations · External hallucinations · Visual recursion · Auditory hallucinations · Environmental orbism / cubism · Object activation · Visual scenery slicing · Perspective hallucinations · Olfactory hallucination
Body scan awareness · Stimulation · Body schema distortion · Muscle relaxation · Nausea · Tingling / electric sensations · Vibrations / buzzing · Physical fatigue · Insomnia · Appetite suppression · Laughter fits · Sedation · Bodily heaviness · Muscle tension · Watery eyes · Increased urination · Dizziness · Headache · Wakefulness · Bodily pressures · Heart rate perception changes · Restlessness · Tactile euphoria · Yawning · Excessive sweating · Trembling · Dry mouth · Bodily lightness · Pain suppression · Breathing alteration · Kundalini-like energy · Nasal congestion · Salivation · Bruxism · Brain zaps · Vomiting · Involuntary body movements · Nystagmus (eye wobbles) · Seizure threshold reduction · Bodily dissociation · Tactile hallucination
Muscle relaxation · Nausea · Tingling / electric sensations · Vibrations / buzzing · Physical fatigue · Insomnia · Appetite suppression · Laughter fits · Sedation · Bodily heaviness · Muscle tension · Watery eyes · Increased urination · Dizziness · Headache · Wakefulness · Bodily pressures · Heart rate perception changes · Restlessness · Tactile euphoria · Yawning · Excessive sweating · Trembling · Dry mouth · Bodily lightness · Pain suppression · Breathing alteration · Kundalini-like energy · Nasal congestion · Salivation · Bruxism · Brain zaps · Vomiting · Involuntary body movements · Nystagmus (eye wobbles) · Bodily dissociation · Tactile hallucination
Conceptual thinking · Cognitive euphoria · Thought connectivity · Pattern recognition enhancement · Cognitive flexibility · Openness enhancement · Aesthetic enhancement · Multiple thought streams · Language suppression · Memory suppression · Thought loops · Confusion · Increased nature relatedness · Synchronicity · Focus suppression · Cognitive impairment · Creativity enhancement · Humor enhancement · Thought deceleration · Thought acceleration · Thought disorganization · Memory fragmentation · Memory replays · Information processing suppression · Cognitive fatigue · Thought organization · Analysis enhancement · Information processing enhancement · Delusions
Pattern recognition enhancement · Cognitive flexibility · Openness enhancement · Aesthetic enhancement · Multiple thought streams · Language suppression · Memory suppression · Thought loops · Confusion · Increased nature relatedness · Synchronicity · Focus suppression · Cognitive impairment · Creativity enhancement · Humor enhancement · Thought deceleration · Thought acceleration · Thought disorganization · Memory fragmentation · Memory replays · Information processing suppression · Cognitive fatigue · Thought organization · Analysis enhancement · Information processing enhancement
Euphoria · Emotional lability · Simultaneous emotions · Dysphoria
Trust enhancement · Disinhibition · Sociability enhancement · Flow state · Communication enhancement · Ego inflation · Compulsive behavior reduction · Boundary dissolution · Identity alteration · Ego dissolution
Communication enhancement · Ego inflation · Compulsive behavior reduction · Boundary dissolution · Identity alteration · Ego dissolution
Time cessation
Non-dual awareness · Entity contact · Death-rebirth sequence
Recursive awareness
Timeline
First alerts emerge as a subtle shift in body awareness — slight tingling, mild stomach unease, or a gentle brightening of visual perception. Effects are easily dismissed as anticipation.
Effects build steadily. Nausea peaks during this phase and typically resolves by its end. Colours begin to saturate, yawning intensifies, and the first visual distortions appear.
Full psychedelic intensity. Visual patterning, colour enhancement, time distortion, and thought connectivity are at maximum. Emotional amplification is pronounced.
Effects recede gradually. Visuals lose intensity, thought patterns begin to normalize, and a sense of re-integration emerges. Emotional processing continues — insights from the peak may crystallize during this phase.
A residual state of emotional openness, mild mood elevation, or reflective introspection lasting hours to days. Some individuals report subtle visual after-images or enhanced pattern sensitivity. Appetite and sleep typically normalize within 4–6 hours of the resolution phase.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Low
- Withdrawal
- None
- Tolerance buildup
- rapid
- Tolerance reset
- 7 days
- Physical
- None
- Psychological
- Negligible
- Compulsive redosing
- Negligible
- Dose escalation
- Negligible
- Cross-tol.
- psilo · psilocin · LSD
Toxicity
Acute Toxicity
No lethal dose data exist for 4-AcO-DMT in any species, and the toxic dose in humans is unknown. Computational modeling predicts moderate-to-high acute oral toxicity, low cardiac risk, and no mutagenic or hormone-disrupting activity.[7]
No fatal overdose cases solely attributable to 4-AcO-DMT have been published. The absence of reports does not confirm safety.
Cardiovascular Effects
Elevated heart rate and brief blood pressure rises are expected, consistent with the serotonergic psychedelic class. Computational predictions indicate lower cardiac risk than DMT and 5-MeO-DMT.[7]
Psychological Risks
High doses can produce panic, paranoia, confusion, identity disruption, and ego dissolution. No controlled studies have characterized these risks specifically for 4-AcO-DMT — class-level psilocybin data provide the best available estimates.
Persistent visual disturbances after use — known as HPPD — have been reported with serotonergic psychedelics.[19] By shared active metabolite and class analogy, 4-AcO-DMT carries the same risk. People with personal or family histories of psychosis, schizophrenia, or bipolar disorder face elevated risk of psychotic episode precipitation.safety citation needed
Tolerance and Dependence
Tolerance builds after a single dose as serotonin receptors reduce their sensitivity.[20][21] Full sensitivity returns in about 7 days. Cross-tolerance extends to all classical psychedelics — LSD, psilocybin, DMT, mescaline.[13]
No physical dependence or withdrawal has been documented for serotonergic psychedelics. In animal studies, 4-AcO-DMT produces sustained positive motivation without the rebound effect negativity that drives compulsive use.[6]
Drug Interactions
Tramadol
Tramadol slows serotonin clearance. Combined with 4-AcO-DMT's direct serotonin activation, this creates a confirmed risk of serotonin syndrome[22] — a potentially life-threatening response involving muscle rigidity, overheating, and seizure. Multiple fatalities have been documented from tramadol combined with other serotonergic drugs.[23] This combination is dangerous.
MAOIs
MAOIs block the enzyme that handles roughly 80% of psilocin's breakdown.[15] This dramatically prolongs and intensifies effects while sharply elevating the risk of severe serotonin-related adverse events.[23]
SSRIs and SNRIs
Chronic SSRI use may blunt psychedelic effects through receptor desensitization. Concurrent use also raises the risk of serotonin overload, though no 4-AcO-DMT-specific data exist.
Cannabis
No published interaction data exist. Receptor-level overlap between cannabinoid and serotonin systems suggests potential for unpredictable effects.citation needed
Detection
4-AcO-DMT is not detectable by standard drug screening panels.[24]
Contraindications
Psychiatric vulnerability: Personal or family history of psychotic disorders, schizophrenia spectrum disorders, or bipolar I disorder. Psychedelics can precipitate or worsen psychotic episodes.[23]
Concurrent tramadol use: Serotonin toxicity risk from combined mechanisms. Absolute contraindication.[22]
Concurrent MAOI use: Dangerous intensification of serotonergic effects through blockade of psilocin's primary breakdown pathway.[23][15]
Heart conditions: Elevated heart rate and blood pressure are expected acute effects. Pre-existing cardiovascular disease or conditions predisposing to irregular heart rhythm are relative contraindications.
Seizure disorders: Possible seizure threshold reduction has been reported at the class level for serotonergic psychedelics.safety citation needed
Harm Reduction[edit]
Forms & Identification
4-AcO-DMT is most commonly sold as the fumarate salt — a white to off-white powder or crystalline solid.[25] Standard reagent tests confirm a 4-substituted tryptamine but cannot distinguish psilocin prodrugs from one another. Active doses are measured in milligrams; small measurement errors can shift the experience from mild to overwhelming. Volumetric dosing from a prepared solution is strongly recommended for powder forms. Drug checking services using mass spectrometry provide the most reliable identification.
Guidelines
- Test every batch using reagent kits and, ideally, a drug checking service before use
- Start low. When unfamiliar with the batch or personal sensitivity, begin at the lower end of the common dose range and wait at least 90 minutes before any additional dose
- Measure carefully. Use a milligram-precision scale (0.001 g). Never estimate powder doses by eye
- Prepare the environment. Remove hazards, ensure access to water and comfortable seating, and have a calm playlist ready
- Eat lightly 2–3 hours beforehand. A full stomach may delay onset; an empty stomach may increase nausea
- Clear the schedule. Allow the full duration plus several hours of afterglow. Do not drive or operate machinery
- Have a sitter. A sober, trusted companion can provide reassurance, manage logistics, and intervene if distress escalates
- Surrender to the experience. Resistance to emerging effects — especially at higher doses — frequently amplifies anxiety. Controlled breathing and a change of environment can help redirect difficult moments
Set & Setting
Psychedelic experiences are profoundly shaped by mindset and environment. Choose a calm, familiar space free from obligations or interruptions. A trusted, sober companion is strongly recommended — especially for first experiences or higher doses.
Avoid use during periods of emotional distress, unresolved conflict, or significant anxiety. These states tend to amplify under psychedelics. Physical comfort matters: access to water, soft lighting, blankets, and a prepared playlist can meaningfully ease the experience.
Aftercare & integration. The days following a psychedelic experience are a window for processing what emerged. Journaling, artwork, or voice recording within the first 24 hours can help capture insights before they fade. Discuss the experience with a trusted friend or integration therapist — especially if difficult emotions, unresolved memories, or existential themes surfaced.
Mild mood shifts, reflectiveness, and altered dream activity are common in the days following use and typically resolve within a week. If anxiety, depersonalization, or intrusive thoughts persist beyond two weeks, seek professional support from a therapist experienced with psychedelic integration.
Recovery & Support
Serotonergic psychedelics carry low abuse liability, and compulsive use patterns are rare. Problematic use can develop — particularly when psychedelics are used to escape rather than explore, or when integration is neglected. If use is becoming a way to avoid addressing life circumstances, reducing frequency or pausing entirely is advisable.
Support resources include psychedelic integration circles, harm reduction organizations such as the Zendo Project and DanceSafe, and therapists trained in psychedelic integration. For broader substance use concerns, SAMHSA's National Helpline (1-800-662-4357) provides free, confidential referrals.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Most difficult psychedelic experiences are distressing but not medically dangerous. Seek immediate help if the person is a danger to themselves or others, is completely unresponsive, experiences seizures, shows signs of severe overheating, or has taken a serotonergic combination and develops muscle rigidity, rapid heart rate, and high fever.
Immediate steps:
- 1. Stay with the person. Speak calmly and simply.
- 2. Move them to a quiet, safe space if possible.
- 3. If unresponsive, place them in the recovery position.
- 4. Call emergency services if symptoms escalate or there is any doubt.
- 5. Do not restrain the person unless there is immediate danger of self-harm.
What to tell the dispatcher: Name the substance (4-AcO-DMT, a synthetic psilocin structural analog), estimated dose, time of ingestion, current symptoms, and any other substances taken. Good Samaritan laws in many jurisdictions protect those who call for help during a drug emergency.
Legal Status[edit]
4-AcO-DMT's legal status varies widely — some countries explicitly schedule it, others cover it under structural analog or ester provisions, and others leave it uncontrolled.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States (federal) | Not explicitly scheduled | Not listed in the Controlled Substances Act. Potentially prosecutable under the Federal Analog Act (21 U.S.C. § 813) as a structural analog of psilocin (Schedule I) when intended for human consumption. No known FAA prosecution specific to 4-AcO-DMT as of 2026[8][26] |
| United States (Alabama) | Schedule I | Explicitly named and scheduled under Alabama state law — one of the few US states to list 4-AcO-DMT by name[26] |
| United Kingdom | Class A (Misuse of Drugs Act 1971) | Controlled as an ester of psilocin under MDA 1971 Schedule 2, Paragraph 3, which extends control to "any ester or ether" of listed substances. Also covered by the Psychoactive Substances Act 2016[9] |
| Germany | Anlage I (BtMG) | Controlled under the strictest category of the Betäubungsmittelgesetz, covering esters, ethers, and salts of scheduled indole alkaloids[27] |
| Canada | Not controlled | Not listed in any CDSA schedule (I–VIII). Possession and acquisition are legal. Canada's CDSA lacks a generic analogue provision equivalent to the US Federal Analog Act[27] |
| Australia | Schedule 9 (TGA Poisons Standard) | Highest restriction category — prohibited substance. Manufacture, possession, supply, and use prohibited[27] |
| Sweden | Controlled substance | Among the first Scandinavian countries to schedule novel research chemicals[27] |
Analog and Prodrug Considerations
In the United States, the Federal Analog Act can apply to substances structurally similar to a Schedule I drug when intended for human consumption.[26] As the acetate ester of psilocin, 4-AcO-DMT meets the structural similarity criterion, but enforcement has been inconsistent and no prosecution specific to 4-AcO-DMT has been published. In the United Kingdom, the ester clause in the Misuse of Drugs Act provides unambiguous coverage without analogue reasoning.[9]
references
- [1] ^abcGlatfelter GC, Pottie E, Partilla JS, Sherwood AM, et al. (2022) Structure-Activity Relationships for Psilocybin, Baeocystin, Aeruginascin, and Related Analogues to Produce Pharmacological Effects in Mice — ACS Pharmacology and Translational Science doi:10.1021/acsptsci.2c00177
- [2]
- [3]
- [4]
- [5] ^abNichols DE, Frescas S (1999) Improvements to the Synthesis of Psilocybin and a Facile Method for Preparing the O-Acetyl Prodrug of Psilocin — Synthesis doi:10.1055/s-1999-3490
- [6] ^abcVargas-Perez H, Minauro-Sanmiguel F, Ting-A-Kee R, Grieder TE, Méndez-Díaz M, Próspero-García O, van der Kooy D (2024) Rewarding Effects of the Hallucinogen 4-AcO-DMT Administration and Withdrawal in Rats: A Challenge to the Opponent-Process Theory — Neuroscience Letters doi:10.1016/j.neulet.2023.137597