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2C-B-FLY
2C-B-FLY is a synthetic psychedelic of the phenethylamine class. It is a structurally locked structural analog of 2C-B — the ring system freezes the molecule into the active shape needed to engage serotonin receptors. That activation disrupts sensory filtering and produces the visual distortions and altered thinking characteristic of classical psychedelics.
2C-B-FLY is an emerging synthetic psychedelic of the phenethylamine class. It is a conformationally locked structural analog of 2C-B, distinguished by longer duration and a heavier body feel. 2C-B-FLY is a partial agonist at the 5-HT₂A receptor,[1][2] producing its effects by disrupting serotonin-mediated sensory filtering and cognitive processing.
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Aaron Monte and David Nichols synthesized 2C-B-FLY in 1996[1] as a research tool to map receptor geometry, not as a drug for human use. In 2009, Bromo-DragonFLY was sold mislabelled as 2C-B-FLY, causing hospitalizations and deaths.[2][3] It remains unscheduled in the United States but controlled in Canada, the United Kingdom, and Sweden.[4]
Subjective effects include geometric visual patterns, color enhancement, mood elevation, and physical body load. The experience is more physically grounded and longer-lasting than 2C-B — a weighted, immersive quality from a persistent somatic heaviness beneath the visual and cognitive shifts.[5] Nausea during onset, physical tension, and difficulty sleeping through the extended tail are common undesired effects.
2C-B-FLY does not cause physical dependence,[6] and its toxic dose in humans is unknown. The primary danger is cardiovascular — it strongly constricts blood vessels and raises blood pressure[7] — amplified by its potential to inhibit enzymes that break down serotonin, making combinations with serotonergic drugs life-threatening.[8] No controlled human studies exist; what is known comes from lab measurements, animal tests, and community reports.
History[edit]
Discovery
2C-B-FLY was first synthesized in 1996 by Aaron Monte and David Nichols.[1] By locking the freely rotating methoxy groups of 2C-B into a rigid ring, they created a molecular probe to determine which oxygen geometry was required for serotonin receptor activation. It was a research tool, not a drug candidate.
The 2009 mislabelling crisis
In 2009, a batch of Bromo-DragonFLY — roughly 20 times more potent by weight — was distributed mislabelled as 2C-B-FLY.[2] Users dosing at 2C-B-FLY levels received massive overdoses of a far more dangerous compound, causing hospitalizations, limb ischemia, and deaths.[3] This remains the most consequential safety event in the compound's history.
Regulatory response
The 2009 crisis triggered scheduling actions across multiple countries. Canada listed it in 2016, the United Kingdom controlled it under two laws, and Sweden and Belgium followed.[4] As of 2026, it remains unscheduled under US federal law, though the Federal Analogue Act may apply.[9]
The name FLY comes from the butterfly-like appearance of the bicyclic ring system in two-dimensional diagrams — the two fused rings spread outward like wings. Bromo-DragonFLY takes its name from the same visual convention applied to a more angular, fully aromatic version of the scaffold. Both naming conventions originated in the Nichols laboratory at Purdue.
Chemistry[edit]
Structural class
2C-B-FLY belongs to the phenethylamine class — specifically the 2C-x series of hallucinogenic phenethylamines.[1] Its molecular formula is C₁₂H₁₄BrNO₂ (284.15 g/mol).
A fused ring system called a tetrahydrobenzodifuran locks the oxygen atoms into a fixed geometry, making it a conformationally restricted structural analog of 2C-B.[1] Bromo-DragonFLY is the fully aromatic version of the same scaffold — and is substantially more potent.[10][11]
Pharmacology[edit]
Mechanism of action
2C-B-FLY acts primarily by activating serotonin receptors — the same receptors targeted by 2C-B, LSD, and psilocin.[6] It also binds a second serotonin receptor type that constricts blood vessels, which is the source of its cardiovascular risk.[7][9] Unlike MDMA, it does not flood the brain with dopamine and serotonin — its profile is predominantly hallucinogenic.[7]
Pharmacokinetics
No human pharmacokinetic studies have been published. Community reports indicate an oral experience of 7–12 hours, with onset around 30–60 minutes and peak at 3–5 hours.[12] The liver breaks it down,[13] but genetic variation in metabolic enzymes means some people clear it more slowly and may experience prolonged or intensified effects.[14]
Neuroscience[edit]
Where it acts
No neuroimaging or electrophysiology studies of 2C-B-FLY have been published. As a serotonin receptor agonist, it is expected to act on pyramidal neurons in the prefrontal cortex, flooding the brain with unfiltered sensory information and disrupting the network associated with self-referential thought.citation needed This likely underlies the geometric visual patterns and altered sense of self reported with serotonergic psychedelics.
Why it matters
One widely used model describes psychedelics as weakening the brain's predictive filters, allowing raw sensory input to overwhelm top-down expectations — which aligns with 2C-B-FLY's confirmed serotonin receptor activity.[7] It likely falls within a category of compounds that promote neural rewiring and new synapse formation, though no direct measurements have been made for 2C-B-FLY specifically.[6]
A controlled study of 2C-B found less ego dissolution than psilocybin at comparable intensity,[5] raising the question of whether phenethylamine FLY compounds engage different brain networks than tryptamines. Whether 2C-B-FLY's rigid ring structure extends duration by holding the receptor longer, and whether its additional receptor binding[7] shapes the subjective or safety profile, remain open questions with no published data.
Subjective Effects[edit]
2C-B-FLY is defined by two qualities unusual for a phenethylamine psychedelic: an extended duration and a heavy physical body load. Visual patterns, color shifts, and mood elevation sit against a persistent somatic heaviness — the experience feels weighted and immersive in a way that shorter-acting psychedelics do not.
Within the phenethylamine class, 2C-B-FLY sits between 2C-B and Bromo-DragonFLY — more visual and longer-lasting than the former, substantially less potent and dangerous than the latter. Survey data suggest novel phenethylamines produce experiences distinct from tryptamines and lysergamides,[15] and 2C-B-FLY's rigid molecular structure may further differentiate it from flexible 2C-x compounds.[5]
First synthesized in 1996 by Aaron Monte and David Nichols at Purdue University as a molecular probe of receptor binding geometry,[3] 2C-B-FLY was designed as a research tool rather than a candidate drug. It entered the research chemical market in the mid-2000s, and a 2009 incident in which the far more potent Bromo-DragonFLY was mislabelled as 2C-B-FLY caused hospitalizations and deaths.[4][5] It remains unscheduled in the United States but is controlled in Canada, the United Kingdom, Sweden, and several other jurisdictions.[6]
Subjective effects include geometric visual patterns, color enhancement, mood elevation, and body load. The experience is reported as more physically grounded and sustained than 2C-B — a persistent somatic heaviness beneath the visual and cognitive shifts that gives the compound a weighted, immersive character.[7] Nausea during onset, physical tension, and difficulty sleeping through the extended tail are common unsought effects.
2C-B-FLY produces no physical dependence[8] and the toxic dose is unknown; tolerance develops rapidly after a single dose.[9] The primary risk is cardiovascular — potent 5-HT₂B agonism drives vasoconstriction and blood pressure elevation[1] — compounded by MAO-A inhibition potential that elevates serotonin syndrome risk in combination use.[10] No controlled human studies exist; current understanding rests on in vitro pharmacology, animal assays, and community reports.
History[edit]
Discovery
2C-B-FLY was first synthesized in 1996 by Aaron P. Monte and David E. Nichols at Purdue University.[3] The compound emerged from a systematic investigation of conformationally restricted phenethylamine hallucinogens — by locking the freely rotating methoxy groups of 2C-B into a rigid tetrahydrobenzodifuran ring system, the Nichols laboratory created molecular probes that revealed which oxygen atom geometry was required for serotonin receptor activation. 2C-B-FLY was a research tool designed to answer a structural question, not a candidate therapeutic.
The 2009 mislabelling crisis
2C-B-FLY appeared on the research chemical market in the mid-2000s, attracting interest from users familiar with the 2C-series phenethylamines.citation needed In 2009, a batch of Bromo-DragonFLY — approximately 20 times more potent by weight — was distributed mislabelled as 2C-B-FLY.[4] Users dosing at levels appropriate for 2C-B-FLY received massively excessive amounts of the far more dangerous compound, resulting in hospitalizations, limb ischemia, and deaths.[5] This incident remains the most consequential safety event in the compound's history.
Regulatory response
The 2009 crisis and broader concern over novel psychoactive phenethylamines triggered scheduling actions across multiple jurisdictions. Canada added 2C-B-FLY to Schedule III in 2016; the United Kingdom captured it under both the Misuse of Drugs Act and the Psychoactive Substances Act; Sweden explicitly scheduled it in 2018; and Belgium added it to controlled substances Annex IVB in 2023.[6] As of 2026, the compound remains unscheduled under United States federal law, though the Federal Analogue Act may apply.[2]
The name FLY derives from the butterfly-like appearance of the bicyclic ring system in two-dimensional structural diagrams — the two fused dihydrofuran rings spread outward from the central benzene ring like wings. The fully aromatic analog, Bromo-DragonFLY, takes its DragonFLY name from the same visual convention applied to the more angular, fully unsaturated benzodifuran system. These naming conventions emerged from the Nichols laboratory at Purdue and have persisted throughout the compound's research and recreational history.
Chemistry[edit]
Structural class
2C-B-FLY belongs to the phenethylamine class — specifically the 2C-x series of 2,5-dimethoxy-4-substituted phenethylamines. Its defining structural feature is the incorporation of the 2- and 5-methoxy groups into a tetrahydrobenzodifuran ring system, which locks the oxygen atoms into a fixed spatial orientation relative to the aromatic ring.[3] This makes 2C-B-FLY a conformationally restricted structural analog of 2C-B.
Within the FLY series, the degree of ring saturation determines pharmacological behavior. 2C-B-FLY is the partially reduced (tetrahydro) ethylamine member, retaining approximate equipotency with its flexible parent compound. DOB-FLY adds an α-methyl group (amphetamine backbone), and Bromo-DragonFLY is the fully aromatic benzodifuran analog — substantially more potent due to complete ring aromatization.[11][12]
Molecular structure
| Molecular formula | C₁₂H₁₄BrNO₂ |
| Molecular weight | 284.15 g/mol |
The core structure consists of a benzene ring fused with two dihydrofuran rings (the tetrahydrobenzodifuran system), a bromine atom at the 4-position (equivalent to the 4-position in 2C-B), and a primary amine connected via an ethyl chain. The two fused dihydrofuran rings enforce a near-planar arrangement of the oxygen atoms relative to the aromatic ring, modeling the geometry that the flexible methoxy groups of 2C-B must adopt to activate the 5-HT₂A receptor.[3]
Stereochemistry
2C-B-FLY possesses no stereocenters and exists as a single achiral structure.[6] Unlike DOB-FLY or other amphetamine-type analogs in the series, no enantiomers require consideration for pharmacological interpretation.
Pharmacology[edit]
Mechanism of action
2C-B-FLY acts primarily as a partial agonist at 5-HT₂A receptors — the serotonin receptor subtype responsible for the hallucinogenic effects of 2C-B, LSD, psilocin, and other classical psychedelics.[8] It also binds potently to 5-HT₂B and 5-HT₂C receptors, and activates TAAR1 (TAAR1).[1][2]
The rigid tetrahydrobenzodifuran ring system forces the oxygen atoms into a geometry that mirrors the active binding conformation at 5-HT₂ receptors.[3] This confirms that the spatial arrangement achieved by the locked structure is sufficient for receptor activation — a finding central to understanding how phenethylamine hallucinogens interact with their target.
2C-B-FLY is not a monoamine releaser.[1] Unlike some benzofuran psychoactives (5-APB, 6-APB), it does not cause the dopamine and serotonin flood characteristic of MDMA or amphetamines. Its profile is predominantly hallucinogenic, with a cardiovascular risk component arising from potent 5-HT₂B activity.[1]
In the mouse head-twitch response assay — a validated predictor of human hallucinogenic potency[13] — 2C-B-FLY is approximately equipotent with 2C-B.[11]
Pharmacokinetics
No human pharmacokinetic studies have been published. Onset time, peak blood concentration, oral bioavailability, and plasma half-life remain uncharacterized in humans.
Liver metabolism has been studied in vitro. 2C-B-FLY is broken down by hepatic enzymes — a critical distinction from Bromo-DragonFLY, which resists liver metabolism and persists far longer in the body.[14] The primary metabolic pathways involve hydroxylation and acetylation. MAO-A also participates in metabolism.[14]
Studies of related FLY compounds identified over thirty metabolites and confirmed metabolism through multiple enzyme systems.[15] Genetic variation in metabolic enzymes means some individuals may clear the compound more slowly, potentially experiencing prolonged or intensified effects.[15]
Community reports indicate a total experience of 7–12 hours by oral administration, with onset at 30–60 minutes and peak effects at 3–5 hours.[16] This is notably longer than 2C-B (4–6 hours), consistent with the rigid ring system potentially affecting how long the compound occupies its receptor target.
Neuroscience[edit]
Where it acts
No neuroimaging or electrophysiology studies of 2C-B-FLY have been published. As a serotonin 2A receptor agonist, it is expected to act on the dense population of serotonin receptors on pyramidal neurons in the prefrontal cortex, increasing excitatory signaling and disrupting the default mode network — the brain system associated with self-referential thought and narrative identity.citation needed This disruption likely underlies the experiences of ego dissolution and altered self-boundaries reported with serotonergic psychedelics.
Simultaneously, 5-HT₂A activation reduces thalamic filtering of sensory input, flooding the cortex with unfiltered information that produces geometric visual patterns, synesthetic blending, and heightened perceptual acuity.citation needed
Why it matters
The REBUS (Relaxed Beliefs Under Psychedelics) model offers the most explanatory framework: psychedelics flatten the brain's predictive hierarchy, weakening top-down expectations and allowing raw sensory data greater influence over conscious experience. 2C-B-FLY's 5-HT₂A agonism would engage this mechanism, though its specific profile relative to tryptamine psychedelics is unknown.
As a confirmed 5-HT₂A agonist,[1] 2C-B-FLY also falls within the psychoplastogen category — compounds expected to promote structural neural remodeling including new dendrite growth and synapse formation — though no direct plasticity measurements have been made for this compound.[8]
The controlled human study of 2C-B found less ego dissolution than psilocybin at comparable subjective intensity,[7] raising the question of whether phenethylamine FLY compounds engage different brain network patterns than tryptamines. Whether the rigid tetrahydrobenzodifuran scaffold alters receptor residence time — potentially explaining the longer duration — and whether 2C-B-FLY's TAAR1 binding[1] contributes meaningfully to its subjective or safety profile remain open questions with no published data.
Subjective Effects[edit]
2C-B-FLY's experiential character is shaped by two features unusual for a phenethylamine psychedelic: an extended duration of 7–12 hours and a pronounced physical body load driven by serotonin₂B activity. Set and setting exert strong influence across the entire dose range — the prolonged timeline amplifies both the rewards of careful preparation and the consequences of its absence. No controlled human studies have directly characterized the compound's subjective effects; all experiential data derive from community reports and inference from the parent compound's pharmacology.[7]
Within the phenethylamine class, 2C-B-FLY sits between 2C-B and Bromo-DragonFLY — more visual and longer-lasting than the former, substantially less potent and shorter-acting than the latter. Survey data suggest that novel phenethylamines produce experiential fingerprints distinct from tryptamines and lysergamides,[17] and 2C-B-FLY's rigid molecular scaffold may further differentiate its qualitative profile from flexible 2C-x compounds.
Effect Grid
At common doses (10–18 mg oral), the full psychedelic experience develops. Visual effects become pronounced: geometric patterning overlays surfaces, objects exhibit drifting and morphing, color saturation intensifies markedly, and closed-eye visuals present as complex, evolving geometric structures. Time distortion becomes significant — minutes may feel like hours. Emotional amplification is characteristic, with music, nature, and interpersonal connection taking on heightened meaning. Thought connectivity increases, producing novel associations and occasionally profound introspective insights.
Physically, stimulation is moderate, with noticeable increases in heart rate and blood pressure. Body load is common during the come-up phase: nausea, jaw tension, and a diffuse sense of physical heaviness or energy. The vasoconstrictive properties of the tetrahydrobenzodifuran scaffold may produce cold extremities in some individuals.
The experience spans 7–12 hours from onset to resolution. Sleep is unlikely for 10+ hours after ingestion. Functional impairment is substantial — driving, operating machinery, and complex decision-making are unsafe for the full duration.
Modeled from the effect's dose-dependence curve — not per-substance measurements.
Music enhancement · Visual breathing · Touch enhancement · Tracers · Depth perception distortion · Perspective distortion · Symmetrical texture repetition · Brightness alteration · Environmental patterning · Light sensitivity · Visual morphing · After-images · Auditory enhancement · Peripheral vision distortion · Sound sensitivity · Spatial disorientation · Synesthesia · Vestibular distortion · Visual diffraction · Visual haze / noise · Visual acuity enhancement · Auditory distortion · Auditory misinterpretation · Peripheral misidentification · Proprioceptive distortion · Sleep-transition hallucinations · Visual melting · Visual processing acceleration · Dreaming enhancement · Visual acuity suppression · Olfactory enhancement · Taste enhancement · Tinnitus · Visual magnification · Flashbacks · Object transformations · Internal hallucinations · External hallucinations · Object activation · Visual recursion · Environmental orbism / cubism · Perspective hallucinations · Visual scenery slicing · Visual processing suppression · Auditory hallucinations · Visual flipping · Persisting hallucinations
Depth perception distortion · Perspective distortion · Symmetrical texture repetition · Brightness alteration · Environmental patterning · Light sensitivity · Visual morphing · After-images · Auditory enhancement · Peripheral vision distortion · Sound sensitivity · Spatial disorientation · Synesthesia · Vestibular distortion · Visual diffraction · Visual haze / noise · Visual acuity enhancement · Auditory distortion · Auditory misinterpretation · Peripheral misidentification · Proprioceptive distortion · Sleep-transition hallucinations · Visual melting · Visual processing acceleration · Dreaming enhancement · Visual acuity suppression · Olfactory enhancement · Taste enhancement · Tinnitus · Visual magnification · Flashbacks · Object transformations · Internal hallucinations · External hallucinations · Object activation · Visual recursion · Environmental orbism / cubism · Perspective hallucinations · Visual scenery slicing · Visual processing suppression · Auditory hallucinations · Visual flipping · Persisting hallucinations
Body high · Insomnia · Stimulation · Spontaneous body sensations · Sexual arousal enhancement · Heart rate perception changes · Tactile euphoria · Tingling / electric sensations · Muscle tension · Nausea · Appetite suppression · Dry mouth · Laughter fits · Physical fatigue · Restlessness · Vibrations / buzzing · Bodily pressures · Headache · Dehydration sensation · Bodily lightness · Breathing alteration · Dizziness · Excessive sweating · Motor control impairment · Vasoconstriction · Increased urination · Watery eyes · Body schema distortion · Involuntary body movements · Trembling · Yawning · Bruxism · Diarrhea · Nystagmus (eye wobbles) · Pain suppression · Motor control enhancement · Vomiting · Bodily dissociation · Tactile hallucination
Spontaneous body sensations · Sexual arousal enhancement · Heart rate perception changes · Tactile euphoria · Tingling / electric sensations · Muscle tension · Nausea · Appetite suppression · Dry mouth · Laughter fits · Physical fatigue · Restlessness · Vibrations / buzzing · Bodily pressures · Headache · Dehydration sensation · Bodily lightness · Breathing alteration · Dizziness · Excessive sweating · Vasoconstriction · Increased urination · Watery eyes · Body schema distortion · Involuntary body movements · Trembling · Yawning · Bruxism · Diarrhea · Nystagmus (eye wobbles) · Pain suppression · Motor control enhancement · Vomiting · Bodily dissociation · Tactile hallucination
Introspection enhancement · Openness enhancement · Cognitive euphoria · Cognitive flexibility · Conceptual thinking · Immersion enhancement · Thought connectivity · Thought acceleration · Cognitive fatigue · Increased nature relatedness · Multiple thought streams · Creativity enhancement · Humor enhancement · Memory suppression · Motivation suppression · Analysis enhancement · Cognitive impairment · Confusion · Focus suppression · Memory fragmentation · Synchronicity · Thought disorganization · Thought loops · Information processing enhancement · Language enhancement · Thought deceleration · Analysis suppression · Cognitive dysphoria · Information processing suppression · Memory replays · Focus enhancement · Motivation enhancement · Thought organization · Delusions of sobriety · Language suppression
Cognitive flexibility · Conceptual thinking · Immersion enhancement · Thought connectivity · Thought acceleration · Cognitive fatigue · Increased nature relatedness · Multiple thought streams · Creativity enhancement · Humor enhancement · Memory suppression · Motivation suppression · Analysis enhancement · Cognitive impairment · Confusion · Focus suppression · Memory fragmentation · Synchronicity · Thought disorganization · Thought loops · Information processing enhancement · Language enhancement · Thought deceleration · Analysis suppression · Cognitive dysphoria · Information processing suppression · Memory replays · Focus enhancement · Motivation enhancement · Thought organization · Language suppression
Simultaneous emotions · Anxiety · Catharsis · Dysphoria · Irritability · Anxiety suppression
Irritability · Anxiety suppression
Trust enhancement · Sociability enhancement · Communication enhancement · Flow state · Depersonalization · Automaticity · Communication suppression · Ego inflation · Social disconnection · Boundary dissolution · Ego dissolution · Cognitive disconnection · Identity alteration · Telepathic feelings
Depersonalization · Automaticity · Communication suppression · Ego inflation · Social disconnection · Boundary dissolution · Ego dissolution · Cognitive disconnection · Identity alteration · Telepathic feelings
Time cessation
Death-rebirth sequence · Entity contact
Mindfulness enhancement · Recursive awareness
Timeline
First alerts appear as subtle shifts in color perception, mild mood elevation, and a faint body awareness. Effects are easily dismissed as placebo at this stage.
Effects build steadily with increasing visual shimmering, emerging geometric patterning, and growing emotional sensitivity. Body load peaks during this phase — nausea and physical tension are most prominent here.
Maximum intensity: vivid visual distortions, pronounced time distortion, deep emotional amplification, and heightened thought connectivity. The extended peak is a distinguishing feature of 2C-B-FLY compared to the shorter-peaking 2C-B.
Effects remain clearly present but intensity diminishes from the peak. Visual effects gradually simplify. Cognitive clarity begins to return while emotional openness persists.
A gradual return toward baseline over several hours. Residual visual brightness, mild thought alteration, and gentle mood elevation may persist. Physical tension dissipates.
Residual mood elevation, reflective thinking, and subtle perceptual shifts may continue for 6–24 hours after the primary experience resolves. Sleep quality may be affected on the first night.
⚠ Do not drive or operate heavy machinery until after a full night of sleep following the experience.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- None
- Tolerance buildup
- rapid
- Tolerance reset
- 7 days
- Physical
- None
- Psychological
- Negligible
- Compulsive redosing
- Negligible
- Dose escalation
- Negligible
- Cross-tol.
- LSD · psilo · mesc
Toxicity
Acute toxicity
No lethal dose data for 2C-B-FLY exist in any species, and the toxic dose in humans is unknown.safety citation needed The 2009 deaths attributed to this compound were caused by Bromo-DragonFLY mislabelled as 2C-B-FLY[2][3] — a compound roughly 20 times more potent with a fundamentally different toxicity profile.
Deaths attributed to "2C-B-FLY" in 2009 were caused by Bromo-DragonFLY mislabelled as 2C-B-FLY. The two compounds cannot be distinguished by appearance or standard reagent tests. Analytical verification (GC-MS, LC-MS/MS, or FTIR) is required to confirm identity.
Cardiovascular risk
2C-B-FLY strongly constricts blood vessels and raises blood pressure due to potent serotonin receptor activity.[7] This risk is inherent to the benzodifuran scaffold and warrants particular caution in people with heart conditions or high blood pressure. Long-term activation of the same receptor type is linked to heart valve damage — a risk established for appetite suppressants with similar receptor activity.citation needed
Blood pressure and heart rate increases are expected at recreational doses, consistent with what has been measured with the parent compound 2C-B.[5]
Serotonergic toxicity
2C-B-FLY may inhibit the enzyme that breaks down serotonin in the body.[8] Combined with its direct serotonin receptor activation, this creates two overlapping pathways for dangerous serotonin buildup when taken alongside other serotonergic substances.
Psychological risks
As a serotonergic psychedelic, 2C-B-FLY can produce overwhelming anxiety, paranoid thinking, and deeply distressing altered states — particularly at higher doses or in adverse conditions. The 7–12-hour duration extends the burden of difficult experiences relative to shorter-acting compounds.
Serotonergic psychedelics can trigger psychotic episodes in people with a personal or family history of psychotic disorders. Persistent visual disturbances after the acute effects resolve — a recognized class-wide risk — have not been documented specifically for 2C-B-FLY in published literature.
Tolerance & Dependence
Tolerance develops rapidly, detectable within 24 hours of a single dose,[16] and takes approximately 7 days to fully recover. Complete cross-tolerance exists with LSD, psilocybin, mescaline, and other serotonergic psychedelics.[16]
Serotonergic psychedelics as a class do not produce physical dependence and are not associated with compulsive use patterns.[6] No withdrawal has been documented.
Drug Interactions
Serotonergic combinations
Combining 2C-B-FLY with other serotonergic substances risks a life-threatening condition — dangerous overheating, muscle rigidity, and unstable heart rate — driven by excess serotonin. This risk is amplified by 2C-B-FLY's dual mechanism: direct serotonin receptor activation and potential enzyme inhibition.[8]
Tramadol is particularly dangerous in combination. As a serotonin-active painkiller that also lowers seizure threshold, it creates multiple converging pathways to toxicity when combined with a serotonergic compound that inhibits monoamine oxidase.[17][8]
MAOIs are contraindicated. Since 2C-B-FLY itself shows MAO-A inhibitory potential,[8] adding external MAO inhibition risks precipitating serotonin syndrome.
SSRIs and SNRIs may reduce psychedelic intensity but carry acute serotonin risk, particularly with compounds that inhibit MAO.
Lithium combined with serotonergic psychedelics has been associated with seizures and severe reactions across the class.citation needed
Cannabis
Cannabis can intensify and prolong psychedelic experiences, increase heart rate, and amplify cardiovascular effects. No specific interaction data exist for 2C-B-FLY.
Metabolic interactions
2C-B-FLY is broken down by liver enzymes.[13] Drugs that inhibit those enzymes — including fluoxetine, paroxetine, quinidine, and bupropion — may slow clearance, potentially intensifying or prolonging effects.
Contraindications
9 knownPsychotic disorders: Personal or family history of schizophrenia, schizoaffective disorder, or other psychotic conditions is an absolute contraindication.
Bipolar disorder: Serotonergic psychedelics may trigger manic or mixed episodes.
Heart and circulation conditions: The identified vasoconstriction risk[7] and expected blood pressure effects[5] make uncontrolled high blood pressure, coronary artery disease, peripheral vascular disease, and history of stroke relative-to-absolute contraindications depending on severity.
Concurrent serotonergic medications: MAOIs, SSRIs, SNRIs, tramadol, triptans, and lithium are contraindicated due to serotonin syndrome and interaction risks.[8]
Pregnancy and breastfeeding: No reproductive safety data exist. As a serotonergic agent with blood vessel-constricting properties, use during pregnancy is contraindicated on precautionary grounds.
Seizure disorders: Psychedelics may lower seizure threshold. This risk is amplified when combined with seizure-threshold-lowering agents such as tramadol.
Harm Reduction[edit]
Forms & Identification
The single most important risk with 2C-B-FLY is compound misidentification. The 2009 crisis demonstrated that visual inspection and standard reagent tests cannot distinguish it from Bromo-DragonFLY.[2] Bromo-DragonFLY is active at far lower doses and lasts 2–3 days; dosing it as 2C-B-FLY is life-threatening.
Analytical verification via GC-MS, LC-MS/MS, or FTIR — available through drug checking services in many jurisdictions — is the only reliable method of confirming identity. If testing is unavailable, treat any unverified material with extreme caution and start with a fraction of the intended dose.
Guidelines
- Verify substance identity through analytical testing before use — reagent kits alone cannot distinguish 2C-B-FLY from Bromo-DragonFLY
- Start with a low dose and wait at least 90 minutes before considering redosing — onset can be slow and variable
- Clear the full day of obligations; 7–12 hours is the expected duration, with residual effects possible beyond that
- Have a sober, trusted companion present who is aware of the compound's extended timeline
- Stay hydrated and maintain moderate body temperature — vasoconstriction may impair normal temperature regulation
- Individuals with heart conditions, high blood pressure, or circulation problems should not use this compound
- Keep the environment calm and controllable — have options to change lighting, music, and social contact
- Do not drive or operate machinery for the full duration and recovery period
Set & Setting
The extended duration makes preparation more consequential than with shorter-acting psychedelics. A secure, comfortable, familiar environment with no obligations for the full day is essential. A sober companion who understands the long timeline and potential for physical discomfort can provide reassurance during difficult phases.
Unresolved anxiety, recent emotional upheaval, or unfamiliar social environments increase the likelihood of distress — and the extended duration means difficult states last longer than with 2C-B or most tryptamines.
Aftercare & integration. The extended duration can leave people physically depleted. Prioritize sleep, hydration, and easily digestible food in the 24 hours following a session. Light physical tension or residual body load may persist into the next day — gentle movement and warmth can help.
The experience may surface material that benefits from reflection. Journaling within 24–48 hours while impressions remain vivid can anchor insights. If the experience was distressing, talking with a trusted person or a psychedelic-informed therapist can help. Persistent anxiety, depersonalization, or visual disturbances lasting beyond a few days warrant professional consultation.
Recovery & Support
2C-B-FLY does not produce physical dependence, and compulsive use patterns are rare with serotonergic psychedelics. Any pattern of use that interferes with daily functioning, relationships, or wellbeing deserves attention. Psychedelic integration circles, harm reduction organizations, and substance use counselors familiar with psychedelic experiences can provide non-judgmental support. The Fireside Project (62-FIRESIDE) offers free peer support for people processing difficult psychedelic experiences.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Uncomfortable body load, mild nausea, and anxiety are within the expected range for 2C-B-FLY. Seek immediate help for: chest pain or pressure, severe headache with neck stiffness, numbness or color change in extremities (blue or white fingers/toes), seizures, loss of consciousness, dangerously elevated body temperature, or complete detachment from reality with self-harm risk.
Immediate steps:
- 1. Call emergency services if any of the above symptoms are present
- 2. Place the person in the recovery position if unconscious but breathing
- 3. Keep them cool if overheating; keep them warm if shivering
- 4. Remove hazards from the immediate environment
- 5. Do not restrain unless there is immediate danger of self-harm
- 6. Do not induce vomiting
- 7. Stay with the person until help arrives
What to tell the dispatcher: Name the substance (2C-B-FLY), estimated amount taken, time of ingestion, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during drug emergencies — calling for medical assistance is always the right decision.
Legal Status[edit]
As of April 2026, 2C-B-FLY is explicitly scheduled in several countries, captured by blanket psychoactive substance laws in others, and not specifically controlled under United States federal law.[9]
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Not specifically scheduled | Not listed in federal controlled substances schedules as of June 2025.[9] The Federal Analogue Act (21 U.S.C. § 813) may apply if intended for human consumption, given structural and pharmacological similarity to Schedule I phenethylamines. |
| United Kingdom | Class A / Psychoactive Substances Act | Controlled as Class A under the Misuse of Drugs Act 1971 via structural analogy to 2C-B. Additionally covered by the Psychoactive Substances Act 2016.[4] |
| Canada | Schedule III | Explicitly scheduled since October 31, 2016.[4] |
| Sweden | Scheduled | Explicitly classified as illegal since April 2018.[4] |
| Germany | NpSG controlled | Covered under the Neue-psychoaktive-Stoffe-Gesetz (New Psychoactive Substances Act).[4] |
| Belgium | Annex IVB | Added to controlled substances Annex IVB in 2023.[4] |
| Italy | Schedule I | Illegal to possess, produce, sell, or purchase.[4] |
| Poland | Group II-P (likely) | Considered controlled as a 2,5-dimethoxyphenethylamine derivative.[4] |
Legal status varies by jurisdiction and changes frequently. This information is not legal advice. Verify current local law before any use or possession.
Safety[edit]
- Acute toxicity
- Low
- Chronic toxicity
- Moderate
- Withdrawal
- None
- Tolerance buildup
- rapid
- Tolerance reset
- 7 days
- Physical
- None
- Psychological
- Negligible
- Compulsive redosing
- Negligible
- Dose escalation
- Negligible
- Cross-tol.
- LSD · psilo · mesc
Toxicity
Acute toxicity
No lethal dose data for 2C-B-FLY exist in any species, and no controlled toxicity studies have been conducted. The toxic dose in humans is unknown.safety citation needed
No published case reports document acute poisoning from confirmed 2C-B-FLY. The 2009 deaths commonly attributed to this compound were caused by Bromo-DragonFLY mislabelled as 2C-B-FLY.[4][5] Bromo-DragonFLY is roughly 20 times more potent by weight and metabolically resistant — a fundamentally different toxicity profile. This distinction is critical for accurate risk assessment.
Deaths attributed to "2C-B-FLY" in 2009 were caused by Bromo-DragonFLY mislabelled as 2C-B-FLY. The two compounds cannot be distinguished by appearance or standard reagent tests. Analytical verification (GC-MS, LC-MS/MS, or FTIR) is required to confirm identity.
Cardiovascular risk
2C-B-FLY carries an identified risk for blood vessel constriction, reduced blood flow, and blood pressure elevation due to potent serotonin₂B and 5-HT₂A receptor activity.[1] This vasoconstrictive potential is inherent to the benzodifuran scaffold. While less severe than Bromo-DragonFLY (which has caused documented tissue death in extremities), it warrants concern at higher doses or in individuals with pre-existing heart or circulation conditions.
Long-term 5-HT₂B agonism is associated with heart valve damage — a risk established for the appetite suppressants fenfluramine and dexfenfluramine and relevant to any compound with potent 5-HT₂B activity.citation needed Blood pressure and heart rate increases are expected based on the parent compound 2C-B, which produced measurable effects at 20 mg oral in controlled settings.[7]
Serotonergic toxicity
2C-B-FLY demonstrates potential MAO-A inhibition,[10] an unusual property for a phenethylamine psychedelic. Combined with its direct serotonin receptor activation, this creates a dual mechanism for dangerous serotonin buildup when taken with other serotonergic substances.
Psychological risks
No controlled studies have assessed 2C-B-FLY's psychological risk profile. As a serotonergic psychedelic, it can produce overwhelming anxiety, paranoid thinking, panic, and deeply distressing altered states — particularly at higher doses or in adverse set-and-setting conditions. The 7–12-hour duration extends the temporal burden of difficult experiences relative to shorter-acting compounds.
Serotonergic psychedelics can trigger psychotic episodes in individuals with personal or family history of psychotic disorders. Hallucinogen persisting perception disorder (HPPD) — persistent visual disturbances after acute effects resolve — is a recognized class-wide risk. No 2C-B-FLY-specific cases appear in published literature for either condition.
Tolerance & Dependence
Tolerance develops rapidly via downregulation, detectable within 24 hours of a single dose.[9] Full recovery takes approximately 7 days (tolerance half-life ~3 days). Complete cross-tolerance exists with LSD, psilocybin, mescaline, and other serotonergic psychedelics.[9]
Serotonergic psychedelics as a class do not produce physical dependence and are not associated with compulsive use patterns.[8] No withdrawal has been documented.
Drug Interactions
Serotonergic combinations
Combining 2C-B-FLY with other serotonergic substances presents elevated risk of serotonin syndrome — a potentially fatal condition involving dangerously high body temperature, muscle rigidity, unstable heart rate and blood pressure, and altered consciousness. This risk is amplified by 2C-B-FLY's dual mechanism: direct serotonin receptor activation combined with potential MAO-A inhibition.[10]
Tramadol is particularly dangerous in combination. As a serotonin-active painkiller that also lowers seizure threshold, tramadol combined with a serotonergic psychedelic that inhibits monoamine oxidase creates multiple converging pathways to serotonin syndrome.[18][10]
MAOIs are contraindicated. Since 2C-B-FLY itself shows MAO-A inhibitory potential,[10] adding external MAO inhibition risks precipitating serotonin syndrome.
SSRIs and SNRIs may reduce psychedelic intensity through long-term receptor changes, but acute combinations carry serotonin syndrome risk, particularly with compounds that inhibit MAO.
Lithium combined with serotonergic psychedelics has been associated with seizures and severe reactions across the psychedelic class.citation needed
Cannabis
Cannabis can intensify and prolong psychedelic experiences, increase heart rate, and amplify cardiovascular effects. No specific interaction data exist for 2C-B-FLY with cannabis.
Metabolic interactions
Because 2C-B-FLY is metabolized by liver enzymes,[14] co-administration with potent inhibitors of those enzymes (including fluoxetine, paroxetine, quinidine, and bupropion) may slow clearance and prolong or intensify effects.
Contraindications
9 knownPsychotic disorders: Personal or family history of schizophrenia, schizoaffective disorder, or other psychotic conditions is an absolute contraindication.
Bipolar disorder: Serotonergic psychedelics may trigger manic or mixed episodes.
Heart and circulation conditions: The identified vasoconstriction risk[1] and expected blood pressure effects[7] make uncontrolled high blood pressure, coronary artery disease, peripheral vascular disease, and history of stroke relative-to-absolute contraindications depending on severity.
Concurrent serotonergic medications: MAOIs, SSRIs, SNRIs, tramadol, triptans, and lithium are contraindicated due to serotonin syndrome and other interaction risks.[10]
Pregnancy and breastfeeding: No reproductive safety data exist. As a serotonergic agent with blood vessel-constricting properties, use during pregnancy is contraindicated on precautionary grounds.
Seizure disorders: Psychedelics may lower seizure threshold. This risk is amplified when combined with seizure-threshold-lowering agents such as tramadol.
Harm Reduction[edit]
Forms & Identification
The single most important risk with 2C-B-FLY is compound misidentification. The 2009 crisis — in which Bromo-DragonFLY was sold as 2C-B-FLY — demonstrated that visual inspection and standard reagent testing cannot reliably distinguish the two compounds.[4] Bromo-DragonFLY is active at far lower doses and lasts 2–3 days; dosing it as though it were 2C-B-FLY is life-threatening.
Analytical verification via GC-MS, LC-MS/MS, or FTIR — available through drug checking services in many jurisdictions — is the only reliable method of confirming identity. If analytical testing is unavailable, treat any unverified material with extreme caution and start with a fraction of the intended dose.
Guidelines
- Verify substance identity through analytical testing before use — reagent kits alone cannot distinguish 2C-B-FLY from Bromo-DragonFLY
- Start with a low dose and wait at least 90 minutes before considering redosing — onset can be slow and variable
- Clear the full day of obligations; 7–12 hours is the expected duration, with residual effects possible beyond that
- Have a sober, trusted companion present who is aware of the compound's extended timeline
- Stay hydrated and maintain moderate body temperature — vasoconstriction may impair normal temperature regulation
- Individuals with heart conditions, hypertension, or circulation problems should not use this compound
- Keep the environment calm and controllable — have options to change lighting, music, and social contact
- Do not drive or operate machinery for the full duration and recovery period
Set & Setting
The 7–12-hour duration makes environmental preparation more consequential than with shorter-acting psychedelics. A secure, comfortable, and familiar environment with no obligations for the full day is essential. A trusted, sober companion who understands the compound's long timeline and potential for physical discomfort can provide reassurance during difficult phases.
Psychological preparation matters equally. Unresolved anxiety, recent emotional upheaval, or unfamiliar social environments increase the likelihood of a distressing experience — and the extended duration means difficult psychological states persist longer than with 2C-B or most tryptamines.
Aftercare & integration. The extended duration of 2C-B-FLY can leave users physically depleted. Prioritize sleep, hydration, and easily digestible food in the 24 hours following a session. Light physical tension or residual body load may persist into the next day — gentle movement and warmth can help.
Psychologically, the experience may surface material that benefits from reflection. Journaling within 24–48 hours while impressions remain vivid can anchor insights. If the experience was distressing, talking with a trusted person or a psychedelic-informed therapist can help process difficult content. Persistent anxiety, depersonalization, or visual disturbances lasting beyond a few days warrant professional consultation.
Recovery & Support
2C-B-FLY does not produce physical dependence, and compulsive use patterns are rare with serotonergic psychedelics. However, any pattern of use that interferes with daily functioning, relationships, or wellbeing deserves attention. Psychedelic integration circles, harm reduction organizations, and substance use counselors familiar with psychedelic experiences can provide non-judgmental support. The Fireside Project (62-FIRESIDE) offers free peer support for people processing difficult psychedelic experiences.
Recovery resources, crisis lines, and support pathways → View all
Emergency Response
Recognizing an emergency: Uncomfortable body load, mild nausea, and anxiety are within the expected range for 2C-B-FLY. Seek immediate help for: chest pain or pressure, severe headache with neck stiffness, numbness or color change in extremities (blue or white fingers/toes), seizures, loss of consciousness, dangerously elevated body temperature, or complete detachment from reality with self-harm risk.
Immediate steps:
- 1. Call emergency services if any of the above symptoms are present
- 2. Place the person in the recovery position if unconscious but breathing
- 3. Keep them cool if overheating; keep them warm if shivering
- 4. Remove hazards from the immediate environment
- 5. Do not restrain unless there is immediate danger of self-harm
- 6. Do not induce vomiting
- 7. Stay with the person until help arrives
What to tell the dispatcher: Name the substance (2C-B-FLY), estimated amount taken, time of ingestion, and current symptoms. Good Samaritan laws in many jurisdictions protect people who call for help during drug emergencies — calling for medical assistance is always the right decision.
Legal Status[edit]
As of April 2026, 2C-B-FLY occupies a fragmented legal landscape: explicitly scheduled in several countries, captured by blanket psychoactive substance legislation in others, and not specifically controlled under United States federal law. Its legal trajectory has been shaped primarily by the broader regulatory response to novel psychoactive phenethylamines and the 2009 safety crisis involving Bromo-DragonFLY mislabelling.
| Jurisdiction | Classification | Key provisions |
|---|---|---|
| United States | Not specifically scheduled | Not listed in federal controlled substances schedules as of June 2025.[2] The Federal Analogue Act (21 U.S.C. § 813) may apply if intended for human consumption, given structural and pharmacological similarity to Schedule I phenethylamines. |
| United Kingdom | Class A / Psychoactive Substances Act | Controlled as Class A under the Misuse of Drugs Act 1971 via structural analogy to 2C-B. Additionally covered by the Psychoactive Substances Act 2016.[6] |
| Canada | Schedule III | Explicitly scheduled since October 31, 2016.[6] |
| Sweden | Scheduled | Explicitly classified as illegal since April 2018.[6] |
| Germany | NpSG controlled | Covered under the Neue-psychoaktive-Stoffe-Gesetz (New Psychoactive Substances Act).[6] |
| Belgium | Annex IVB | Added to controlled substances Annex IVB in 2023.[6] |
| Italy | Schedule I | Illegal to possess, produce, sell, or purchase.[6] |
| Poland | Group II-P (likely) | Considered controlled as a 2,5-dimethoxyphenethylamine derivative.[6] |
The EMCDDA first received notification of 2C-B-FLY through its early warning system in 2007,[6] with multiple subsequent notifications. The Center for Forensic Science Research and Education first detected 2C-B-FLY in evidence materials in California in February 2025.[2] Legal status in Australia, New Zealand, France, Spain, the Netherlands, and other jurisdictions should be verified locally.
Frequently asked questions
What is 2C-B-FLY?
2C-B-FLY is a synthetic phenethylamine psychedelic featuring a rigid tetrahydrobenzodifuran ring system, first synthesized in 1996 at Purdue University. It acts as a 5-HT₂A partial agonist approximately equipotent with 2C-B but with a notably longer duration of 7–12 hours.
How long does 2C-B-FLY last?
Total duration by route of administration — Oral: 7 – 12 hours. Ranges vary with dose and individual factors; see the duration table for onset, peak, and after-effect phases.
Where can I find dosage information for 2C-B-FLY?
Psychedex publishes a dosage table for 2C-B-FLY on this page covering these routes of administration: oral. Dose values are presented only in that table, always alongside their route of administration.
What are dangerous combinations with 2C-B-FLY?
The highest-severity documented interactions for 2C-B-FLY: MAOIs (Lethal), Buspirone (Dangerous), Dopamine agonists (Dangerous), GHB, Baclofen (Dangerous), GHB, GBL (Dangerous). See the interactions section for the full list with mechanisms and severity levels.
Is 2C-B-FLY addictive?
Psychedex records tolerance and dependence data rather than a yes/no rating. Recorded tolerance indicators for 2C-B-FLY: tolerance builds rapid; full reset takes 7 days; cross-tolerance develops with LSD, psilocybin, mescaline, DMT, 2C-B, DOB, DOI, DOC. See the article's dependence and safety sections for recorded dependence data.
experience reports
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First-person accounts of subjective effects, timing, and outcomes — submitted for harm reduction.
references
- [1] ^abcdMonte AP, Marona-Lewicka D, Parker MA, Wainscott DB, Nelson DL, Nichols DE (1996) Dihydrobenzofuran analogues of hallucinogens. 3. Models of 4-substituted (2,5-dimethoxyphenyl)alkylamine derivatives with rigidified methoxy groups — Journal of Medicinal Chemistry PMID:8709129
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