5-APB
5-(2-aminopropyl)benzofuran
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5-APB (5-(2-aminopropyl)benzofuran) — Benzofury — is a synthetic entactogen-stimulant of the benzofuran class. It is a close structural analog of MDA, with stronger psychedelic character than MDMA.[1][2] It floods the brain with serotonin, dopamine, and norepinephrine, combining entactogenic warmth with mild psychedelic effects.[3]
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MDMA, MDA, 6-APB +2 moreMDMA, MDA, 6-APB, 5-MAPB, 6-MAPB show less
David Nichols first synthesized 5-APB around 1993 as a potentially safer alternative to MDMA.[4] It entered recreational markets in 2010 as "Benzofury," sold interchangeably with related benzofuran compounds, primarily in the United Kingdom. It is now a controlled substance in the UK and Germany, with no approved medical use and no human clinical trials.
Subjective effects include emotional warmth, empathogenic openness, sensory enhancement, mild geometric visuals, and cognitive euphoria. The experience sits between MDMA and MDA — more perceptually active and introspective than MDMA, warmer and more sociable than a classical psychedelic. Nausea, jaw tension, and comedown anxiety are common; a multi-day period of low mood and fatigue typically follows.
Dependence is moderate, comparable to MDMA; the lethal dose is unknown, with only two documented human deaths to bracket the range.[5][6] The greatest long-term risk is heart valve damage from sustained serotonin receptor activation,[7][2] and a triple serotonergic mechanism makes poisoning easier to trigger than with MDMA.[3] Understanding rests almost entirely on cell studies, animal data, and case reports — no controlled human trials exist.
History[edit]
Discovery
5-APB was first synthesized around 1993 by David Nichols as a potentially non-neurotoxic alternative to MDMA[4] — replacing a key part of MDA's structure with a benzofuran oxygen atom to preserve entactogenic effects while reducing toxicity. A patent covering 5-APB and 6-APB was filed around 2000 by Eli Lilly researchers investigating the compounds as potential therapeutics.[4] citation needed
Market emergence
5-APB appeared on the research chemical market in 2010, detected by European drug monitoring agencies,[4] and sold under the "Benzofury" label alongside 6-APB as a legal MDMA alternative, predominantly in the United Kingdom.[8] Products under this label frequently contained variable and undisclosed compounds, making it impossible to attribute specific effects or harms to 5-APB alone.[8]
Prohibition and current status
The UK issued a temporary ban on 5-APB and related benzofurans in June 2013,[9] permanently classifying it as Class B a year later,[8] while Germany scheduled it in July 2013.[4] The first documented fatality appeared in 2014,[6] and the definitive pharmacological profile was established by Rickli et al. in 2015.[2]
The name "Benzofury" became the dominant market identity for the entire aminoalkylbenzofuran family during 2010–2013. In practice, the label covered multiple compounds — 5-APB, 6-APB, 5-MAPB, 6-MAPB — sold interchangeably, making "Benzofury" more brand than substance identifier. The naming ambiguity persists in harm reduction discussions, where users sometimes conflate the pharmacologically distinct isomers.
Chemistry[edit]
5-APB belongs to the aminoalkylbenzofuran class — a chemical family built by replacing the methylenedioxy bridge of MDA with a single benzofuran oxygen atom.[10] Its molecular formula is C₁₁H₁₃NO (molecular weight 175.23 g/mol).
The "5" in its name indicates where the aminopropyl side chain attaches on the benzofuran ring — the same positional difference that distinguishes it from its isomer 6-APB, which has meaningfully different pharmacological and toxicological properties despite an identical molecular formula.
Pharmacology[edit]
Mechanism of action
5-APB works by reversing the brain's serotonin, dopamine, and norepinephrine transporters — instead of blocking reuptake, it forces these chemicals to flood into the synapse.[2][1] This mechanism is shared with MDMA and MDA, but 5-APB adds two further layers on top of it.
Beyond transporter reversal, 5-APB directly activates serotonin receptors with greater potency than MDMA[3] and inhibits the enzyme that breaks serotonin down after release.[3] This triple action — release, receptor activation, and slower breakdown — places it pharmacologically closer to MDA than to MDMA, confirmed by animal studies.[1]
Pharmacokinetics
No human pharmacokinetic data exist for 5-APB. The closest structural analog with human data, 5-MAPB, showed a half-life of approximately 6.5 hours in a clinical case — comparable to MDMA.[11] Critically, liver metabolism of 5-APB generates toxic byproducts rather than simply clearing the drug; blocking the responsible enzyme reduced liver cell damage in laboratory models.[12]
Neuroscience[edit]
Where it acts
No brain imaging data exist for 5-APB in humans. Based on its pharmacology, it activates the same neural circuits as MDMA and MDA: serotonin release reduces fear reactivity and increases emotional openness, dopamine release activates reward pathways, and norepinephrine drives physical arousal.[13]
Why it matters
5-APB's stronger serotonin receptor activation compared to MDMA[3] predicts greater cortical arousal — the cellular trigger for psychedelic-like perceptual effects, consistent with 5-APB's MDA-like character. Its serotonin-preferring profile produces stronger empathogenic effects than pure stimulants while retaining moderate reward pathway activation.[14][13]
Whether 5-APB promotes neuroplasticity as MDMA does via BDNF expression is unknown. Whether its MAO-A inhibition persists beyond the acute experience — extending the interaction risk window — has not been tested. Whether chronic use produces detectable heart valve damage remains the highest-priority unanswered question given the compound's potent serotonin receptor activation.
Subjective Effects[edit]
5-APB blends entactogenic warmth with a mild psychedelic edge. In social settings, emotional openness and sensory richness dominate; in quiet environments, the perceptual and introspective dimensions come forward. The overall character is warmer than a classical psychedelic and more visually active than MDMA.
It sits closest to MDA in feel — more introspective and perceptually rich than MDMA, with a greater capacity for visual distortion and inner depth. Users report it as longer-lasting and more stimulating than MDMA, with the psychedelic character becoming more pronounced at higher amounts.
Effect Grid
At common doses (approximately 50–80 mg oral), the full entactogenic experience manifests. Empathy enhancement is prominent — emotional barriers diminish, and interpersonal connection feels deeply facilitated. Cognitive euphoria is strong and sustained. Music enhancement reaches its characteristic peak, with complex emotional responses to sound. Sensory perception intensifies across modalities, with colour saturation and tactile sensitivity notably increased.
Physically, stimulation is pronounced: elevated heart rate and blood pressure, excessive sweating, significant jaw clenching, and muscle tension throughout the body. Wakefulness is enforced — sleep is impossible during effects. Appetite is fully suppressed. Nausea may occur during the come-up.
The experience commits approximately 6–8 hours including the come-up, peak, and offset. A comedown phase with cognitive fatigue, irritability, and low mood may follow for 1–3 days.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Light sensitivity · Sound sensitivity · After-images · Color alteration · Tracers · Visual processing acceleration · Auditory distortion · Geometry · Synesthesia · Visual breathing · Visual drifting
Tracers · Visual processing acceleration · Auditory distortion · Geometry · Synesthesia · Visual breathing · Visual drifting
Pupil dilation · Body scan awareness · Appetite suppression · Spontaneous body sensations · Tactile euphoria · Insomnia · Muscle tension · Bruxism · Dry mouth · Physical fatigue · Excessive sweating · Dehydration sensation · Heart rate perception changes · Laughter fits · Nystagmus (eye wobbles) · Bodily lightness · Restlessness · Tingling / electric sensations · Vibrations / buzzing · Nausea · Sexual arousal suppression · Headache · Dizziness · Trembling · Vomiting · Yawning
Tactile euphoria · Insomnia · Muscle tension · Bruxism · Dry mouth · Physical fatigue · Excessive sweating · Dehydration sensation · Heart rate perception changes · Laughter fits · Nystagmus (eye wobbles) · Bodily lightness · Restlessness · Tingling / electric sensations · Vibrations / buzzing · Nausea · Sexual arousal suppression · Headache · Dizziness · Trembling · Vomiting · Yawning
Introspection enhancement · Thought acceleration · Immersion enhancement · Cognitive fatigue · Novelty enhancement · Motivation enhancement · Humor enhancement · Focus enhancement · Cognitive flexibility · Creativity enhancement · Language enhancement · Thought connectivity · Analysis enhancement · Information processing enhancement · Motivation suppression · Conceptual thinking · Increased nature relatedness · Pattern recognition enhancement · Memory enhancement · Thought organization · Thought deceleration
Novelty enhancement · Motivation enhancement · Humor enhancement · Focus enhancement · Cognitive flexibility · Creativity enhancement · Language enhancement · Thought connectivity · Analysis enhancement · Information processing enhancement · Motivation suppression · Conceptual thinking · Increased nature relatedness · Pattern recognition enhancement · Memory enhancement · Thought organization · Thought deceleration
Anxiety suppression · Catharsis · Irritability · Anhedonia · Anxiety · Emotional lability · Simultaneous emotions · Dysphoria
Anxiety · Emotional lability · Simultaneous emotions · Dysphoria
Sociability enhancement · Emotional susceptibility · Flow state · Craving · Boundary dissolution
Boundary dissolution
Timeline
First alerts emerge as a gentle body warmth and subtle mood lift. Physical awareness increases slightly — a faint tingle or stomach flutter signals absorption.
Stimulation builds noticeably: heart rate rises, jaw tension begins, and sociability increases. Nausea may occur during this phase. Emotional openness starts to emerge.
Full entactogenic plateau with prominent empathy enhancement, cognitive euphoria, and music enhancement. Stimulation is strong — elevated heart rate, sweating, pronounced mydriasis. Emotional depth and sensory richness are at maximum.
Intensity subsides gradually from peak. Entactogenic warmth persists but cognitive sharpness begins to return. Stimulation remains elevated.
Effects recede to a residual stimulation with mild mood elevation. Physical tension eases. Appetite may begin to return.
A comedown lasting 1–3 days characterised by cognitive fatigue, low mood, irritability, and disrupted sleep. Serotonin depletion underlies these residual effects, which are more pronounced after higher doses or repeated use.
⚠ Do not drive or operate machinery until mood and cognitive function have fully returned to baseline — fatigue and impaired concentration may persist for 24–48 hours.
Safety[edit]
- Acute toxicity
- High
- Chronic toxicity
- High
- Withdrawal
- Mild
- Tolerance buildup
- moderate
- Tolerance reset
- 10 days
- Physical
- Low
- Psychological
- Moderate
- Compulsive redosing
- Low
- Dose escalation
- Moderate
- Cross-tol.
- MDMA · MDA · 6-APB
Toxicity
Lethal dose
The toxic dose of 5-APB in humans is unknown. No LD₅₀ data specific to 5-APB have been published; the closely related 5-MAPB shows a narrower safety margin than MDMA in mice.[15] Two fatal human cases define the only known concentration range:
- 0.86 mg/L — 25-year-old male; 5-APB as primary agent with low-level alcohol and trace THC[5]
- 5.6 mg/L — mixed intoxication with approximately 400 mg 5-APB, approximately 500 mg 3-MMC, and alcohol; cardiovascular collapse approximately four hours after ingestion[6]
Liver damage
5-APB is more toxic to liver cells than its isomer 6-APB, and more hepatotoxic than MDMA in isolated cell models.[12][16] The liver's own processing of 5-APB generates reactive toxic intermediates rather than simply clearing the drug.[12]
Heart damage
5-APB potently activates the serotonin receptor responsible for drug-induced heart valve disease — the same mechanism behind valve damage caused by fenfluramine and methysergide — at very low concentrations.[7][2] Sustained activation causes heart valve tissue to thicken and scar.[17][2]
Psychological risks
High doses can produce agitation, disorientation, anxiety, panic, confusion, paranoia, and hallucinations.[11][8] A comedown lasting several days — low mood, irritability, and cognitive fatigue — follows, reflecting serotonin depletion after massive release.[8]
No data exist on whether 5-APB can trigger lasting psychiatric conditions. Its serotonin receptor activity suggests a non-zero risk of persistent visual disturbances (HPPD), though no cases have been reported.
Tolerance and dependence
No tolerance studies specific to 5-APB exist. Tolerance is expected to follow MDMA-class patterns: serotonin depletion reduces the effect of subsequent doses until stores rebuild. Community-derived estimates suggest roughly 5 days to half-reset and 1.5 weeks to full reset. inferred
Cross-tolerance with other serotonin-releasing agents — MDMA, MDA, 6-APB — is expected. Dependence liability is moderate and comparable to MDMA: 5-APB fully substitutes for MDMA in rat studies,[14] and related benzofurans show addictive properties tied to dopamine signaling.[13]
Drug interactions
5-APB releases serotonin, directly activates serotonin receptors, and inhibits the enzyme that breaks serotonin down[3] — making serotonin overload easier to trigger than with MDMA. Its acute toxicity pattern already resembles serotonin syndrome: high body temperature, muscle jerking, agitation, confusion.[11]
Serotonergic drugs (SSRIs, SNRIs, MAOIs, lithium, triptans, tramadol) are the highest-risk class; MAOIs are absolutely contraindicated.[3] Tramadol is flagged as potentially lethal.safety citation needed Alcohol was present in both documented fatalities[5][6] and compounds heat and seizure risk. Other stimulants add cardiovascular strain; 3-MMC co-use resulted in cardiovascular collapse.[6]
Contraindications
Heart conditions (valve disease, arrhythmia, conditions predisposing to cardiac scarring), liver disease, and any ongoing serotonergic medication (MAOIs, SSRIs, SNRIs, lithium, triptans) are absolute contraindications.[7][2][12][3] Seizure disorders and medications that lower the seizure threshold (tramadol, bupropion) significantly elevate risk.[6] Pregnancy is contraindicated by class analogy with amphetamines and MDMA. inferred
Harm Reduction[edit]
Forms & Identification
Products sold as 5-APB have historically contained multiple benzofuran compounds interchangeably — 5-APB, 6-APB, 5-MAPB, 6-MAPB — particularly during the Benzofury era.[8] Reagent testing can confirm a benzofuran class compound but cannot reliably distinguish between isomers.
The isomers differ meaningfully in toxicity — 5-APB is more damaging to liver cells than 6-APB.[12] Laboratory analysis is the only reliable way to confirm isomer identity and purity.
Guidelines
- Test the substance. Reagent kits confirm the general benzofuran class; laboratory analysis confirms the specific isomer. Do not assume a product labeled "5-APB" or "Benzofury" contains only 5-APB.
- Start low. The dose-response curve is uncharacterized. Begin at the lowest reported active dose and wait the full onset period (up to 90 minutes orally) before reassessing.
- Do not redose. The long duration and MAO-A inhibition mean a second dose compounds both serotonergic load and cardiovascular strain disproportionately.
- Stay cool and hydrated. Maintain access to water and a cool environment. Avoid prolonged physical exertion without breaks.
- Space sessions widely. Serotonin depletion requires weeks to recover. A minimum of one month between uses is a conservative baseline; longer is better for both neurotoxicity risk and tolerance.
- Inform a sober person of what has been taken, how much, and when.
Set & Setting
5-APB's character is strongly shaped by environment. Entactogenic warmth dominates in social settings; visual and introspective features become more prominent in quiet environments. Plan for a full day with no obligations — the experience runs 6–8 hours with residual effects beyond.
A trusted, sober companion provides an important safety margin given the compound's capacity for disorientation and anxiety. The physical environment should be temperature-controlled, as 5-APB impairs the body's thermoregulation.
Aftercare & integration. The serotonin depletion following 5-APB use produces a comedown lasting several days — low mood, irritability, difficulty concentrating, and disrupted sleep. This is neurochemical, not psychological: serotonin stores need time to rebuild.
Prioritize sleep, nutritious food, gentle physical activity, and social connection during recovery. Avoid major decisions during the comedown period. If low mood persists beyond one week, or unusual perceptual disturbances appear, consult a healthcare professional.
Recovery & Support
Compulsive use patterns with 5-APB are uncommon but possible — the dopaminergic component provides reinforcement, and psychological habituation to the entactogenic state can develop. If use has become a regular pattern despite negative consequences, or if increasing doses are needed for the same effect, professional support is warranted.
Substance use counseling, cognitive-behavioral therapy, and peer support groups experienced with stimulant or entactogen use are appropriate starting points. No 5-APB-specific treatment protocols exist; approaches used for MDMA-related concerns apply.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: body temperature perceptible through clothing. Seizures. Loss of consciousness. Chest pain or irregular heartbeat. Severe confusion or inability to communicate. Muscle rigidity with jerking movements (a sign of serotonin syndrome).
Immediate steps:
- 1. Call emergency services immediately if any of the above are present.
- 2. Move the person to a cool environment and remove excess clothing.
- 3. If unconscious but breathing, place in the recovery position (on their side, airway clear).
- 4. Do not induce vomiting. Do not restrain the person unless they are in immediate physical danger.
- 5. Monitor breathing continuously until help arrives.
What to tell the dispatcher: Name the substance (5-APB or benzofuran), the estimated amount, the time of ingestion, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during a drug emergency.
No specific reversal agent exists for 5-APB toxicity. Treatment is supportive — cooling, sedation, and monitoring.
Legal Status[edit]
5-APB is explicitly scheduled in the UK and Germany; in other jurisdictions it falls under structural analog provisions or is not specifically addressed by law.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United Kingdom | Class B (Misuse of Drugs Act 1971) | Temporary Class Drug Order from 10 June 2013;[9] permanent Class B from 10 June 2014.[8] Psychoactive Substances Act 2016 provides additional blanket coverage. |
| Germany | Anlage II BtMG (Schedule II) | Listed from 17 July 2013. Available by prescription only with strict controls.[4] |
| United States | Not explicitly scheduled | Likely covered by the Federal Analogue Act as a structural analogue of MDA (Schedule I). No specific DEA scheduling action confirmed.[4] citation needed |
| Australia | Likely covered under analog provisions | Structural similarity to MDA suggests coverage under analog scheduling. Not confirmed from primary government sources. citation needed |
| Canada | Likely covered under analog provisions | Similar compounds may fall under Schedule III. Not confirmed from primary government sources. citation needed |
references
- [1] ^abcBrandt SD, Walters HM, Partilla JS, Blough BE, Kavanagh PV, Baumann MH (2020) The psychoactive aminoalkylbenzofuran derivatives, 5-APB and 6-APB, mimic the effects of 3,4-methylenedioxyamphetamine (MDA) on monoamine transmission in male rats — Psychopharmacology doi:10.1007/s00213-020-05648-z
- [2]
- [3]
- [4]
- [5] ^abcKrpo M, Luytkis HC, Haneborg AM, Høiseth G (2018) A fatal blood concentration of 5-APB — Forensic Science International doi:10.1016/j.forsciint.2018.08.044
- [6]