2C-B-FLY is a psychedelic phenethylamine and the dihydrodifuran analog of 2C-B, in which the two methoxy groups of the parent compound are incorporated into a pair of dihydrofuran rings that "butterfly" around the phenethylamine core — giving the compound its distinctive "FLY" suffix and its common name. It was first synthesized by Aaron Monte and reported in the scientific literature in 1999, predating the broader research chemical boom that would bring phenethylamines to wider public attention.
The compound produces a profound, long-duration psychedelic experience at doses in the 5–15 mg range — making it significantly more potent by weight than 2C-B, which requires 15–30 mg for comparable effects. The experience is characterized by visual phenomena and sensory enhancement similar to other 2C compounds but frequently described as smoother and more aesthetic, with a particular richness of color and geometric patterning. Duration is notably extended compared to 2C-B: 5–8 hours is typical, with lingering perceptual effects potentially extending the total timeline.
A critical safety concern distinguishes 2C-B-FLY from most psychedelics: the dose-response curve is steep and individual sensitivity varies dramatically. Doses that are mildly active for one person can be overwhelming or even medically dangerous for another. Reports of unexpectedly intense experiences at apparently moderate doses have circulated in the harm reduction community, and the compound's cardiovascular effects at high doses appear to be more pronounced than 2C-B. The microdosing community has shown interest in 2C-B-FLY, with reports of subtle perceptual enhancement and mood improvement at sub-threshold doses.
Safety at a Glance
High Risk- Potency Awareness
- Accurate Weighing is Essential
- Toxicity: Overview 2C-B-FLY has limited formal toxicological characterization. The available human safety data consists almost ...
- Overdose risk: Fatal overdose from 2C-B-FLY alone, at doses within the typical recreational range, is extremely ...
If someone is in crisis, call 911 or Poison Control: 1-800-222-1222
Dosage
oral
Duration
oral
Total: 7 hrs – 12 hrsHow It Feels
The onset is notoriously slow. An hour passes, sometimes ninety minutes, with little more to show for it than a faint fluttering in the stomach and a subtle sense that the quality of light in the room has changed. Patience is required, and the temptation to redose during this prolonged come-up has led many users astray. When the effects finally begin to assert themselves, they arrive with a gradual authority -- a steadily building pressure of psychedelic intensity that makes clear the substance has been quietly accumulating force behind the scenes.
By the two-hour mark, the experience has opened into a full psychedelic state of moderate to strong intensity. The visual component is rich and distinctive. Colors are deeply saturated and seem to glow with warm internal light. Geometric patterns emerge in flowing, organic forms -- spiraling, petal-like structures and rounded tessellations that feel botanical in nature, as though the substance is channeling some fundamental plant geometry. Surfaces breathe and flow with a slow, rhythmic cadence. There is a unique tactile dimension to 2C-B-FLY: the skin becomes extraordinarily sensitive, and textures seem to transmit complex information through touch. Fabrics, natural surfaces, and human skin all feel remarkably detailed under the fingertips.
The body load is significant and represents the primary challenge of the experience. There is a heavy, bloated sensation in the abdomen that can escalate into pronounced nausea. Vasoconstriction produces tightness in the chest and coolness in the extremities. Muscle tension settles into the shoulders and neck. The stimulant component is moderate but persistent, generating a restless energy that sits uncomfortably alongside the abdominal heaviness. These physical effects demand a degree of management that can distract from the otherwise rewarding perceptual and emotional content. The headspace is moderately deep -- more introspective and contemplative than the lighter 2C compounds, with the potential for meaningful emotional exploration.
The duration is exceptional. The peak plateau can sustain itself for six to eight hours, and total effects may persist for twelve to sixteen hours. The descent is gradual, with visual effects fading slowly while the body load eases in stages. The aftermath can include lingering fatigue, residual muscle tension, and a heavy, somewhat depleted feeling that may take a full day to resolve. Despite the physical demands, many users find the experience rewarding for its unique visual character, its unusual tactile enhancement, and the sheer depth of the journey that the long duration permits.
Subjective Effects
The effects listed below are based on the Subjective Effect Index (SEI), an open research literature based on anecdotal reports and personal analyses. They should be viewed with a healthy degree of skepticism. These effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects.
Physical Effects
Physical(24)
- Bodily control enhancement— Bodily control enhancement is the subjective feeling of improved physical precision, coordination, a...
- Body load— A diffuse, heavy physical discomfort involving tension, pressure, and malaise in the torso and limbs...
- Dehydration— A state of insufficient bodily hydration manifesting as persistent thirst, dry mouth, and physical d...
- Diarrhea— Diarrhea is the occurrence of frequent, loose, or watery bowel movements as a side effect of certain...
- Difficulty urinating— Difficulty urinating, also known as urinary retention, is the experience of being unable to easily p...
- Excessive yawning— Involuntary, repeated yawning that occurs far more frequently than normal and often without the usua...
- Headache— A painful sensation of pressure, throbbing, or aching in the head that can range from a dull backgro...
- Increased blood pressure— Increased blood pressure (hypertension) is an elevation of arterial pressure above the normal 120/80...
- Increased bodily temperature— Increased bodily temperature (hyperthermia) is an elevation of core body temperature above the norma...
- Increased heart rate— A noticeable acceleration of heartbeat that can range from a subtle awareness of one's pulse to a fo...
- Increased libido— A marked enhancement of sexual desire, arousal, and sensitivity to erotic stimuli that can range fro...
- Muscle cramp— Muscle cramps are sudden, involuntary, and often painful contractions of muscles that occur as a sid...
- Muscle tension— Persistent partial contractions or tightening of muscles that produces uncomfortable stiffness, cram...
- Nausea— An uncomfortable sensation of queasiness and stomach discomfort that may or may not lead to vomiting...
- Physical euphoria— An intensely pleasurable bodily sensation that can manifest as waves of warmth, tingling electricity...
- Pupil dilation— A visible enlargement of the pupil diameter (mydriasis) that can range from subtle widening to drama...
- Sedation— A state of deep physical and mental calming that manifests as a progressive desire to remain still, ...
- Stimulation— A state of heightened physical and mental energy characterized by increased wakefulness, elevated mo...
- Stomach bloating— Stomach bloating is the uncomfortable distension of the abdomen resulting from gas accumulation, flu...
- Stomach cramp— Stomach cramps are sharp, intermittent pains in the abdominal region that can occur when psychoactiv...
- Teeth grinding— An involuntary clenching and rhythmic grinding of the jaw muscles, known clinically as bruxism, that...
- Temperature regulation disruption— Impaired thermoregulation causing unpredictable fluctuations between feeling hot and cold, with risk...
- Vasoconstriction— A narrowing of blood vessels throughout the body that produces sensations of cold extremities, tingl...
- Watery eyes— Excessive tear production causing overflow tearing and blurred vision, commonly occurring during opi...
Tactile(1)
- Tactile enhancement— The sense of touch becomes dramatically heightened, making physical contact feel intensely pleasurab...
Cognitive & Perceptual Effects
Visual(15)
- After images— A visual phenomenon in which a faint, ghostly imprint of a previously viewed image persists in the v...
- Colour enhancement— An intensification of the brightness, vividness, and saturation of colors in the external environmen...
- Colour shifting— The visual experience of colors on objects and surfaces cycling through continuous, fluid transforma...
- Depth perception distortions— Alterations in how the distance of objects within the visual field is perceived, causing layers of s...
- Drifting— The visual experience of perceiving stationary objects, textures, and surfaces as appearing to flow,...
- Geometry— The experience of perceiving complex, ever-shifting geometric patterns superimposed over the visual ...
- Internal hallucination— Vivid, detailed visual experiences perceived within an imagined mental landscape that can only be se...
- Pattern recognition enhancement— An increased ability and tendency to perceive meaningful patterns, faces, and images within ambiguou...
- Perspective distortions— Distortion of perceived depth, distance, and size of real objects, making things appear closer, furt...
- Perspective hallucination— A hallucinatory phenomenon in which the observer's visual perspective shifts from the normal first-p...
- Settings, sceneries, and landscapes— The perceived environment in which hallucinatory experiences take place, ranging from recognizable l...
- Symmetrical texture repetition— Textures appear to mirror and tessellate across surfaces in intricate, self-similar symmetrical patt...
- Tracers— Moving objects leave visible trails of varying length and opacity behind them, similar to long-expos...
- Transformations— Objects and scenery undergo perceived visual metamorphosis, smoothly shapeshifting into other recogn...
- Visual acuity enhancement— Vision becomes sharper and more defined than normal, as though a slightly blurry lens has been broug...
Cognitive(16)
- Anxiety— Intense feelings of apprehension, worry, and dread that can range from a subtle background unease to...
- Cognitive fatigue— Mental exhaustion and difficulty sustaining thought after intense cognitive experiences, common duri...
- Conceptual thinking— A shift in the nature of thought from verbal, linear sentence structures to intuitive, non-linguisti...
- Confusion— An impairment of abstract thinking marked by a persistent inability to grasp or comprehend concepts ...
- Creativity enhancement— An increase in the ability to imagine new ideas, overcome creative blocks, think about existing conc...
- Delusion— A delusion is a fixed, false belief that is held with unshakeable certainty and is impervious to con...
- Disinhibition— A marked reduction in social inhibitions, self-consciousness, and behavioral restraint that manifest...
- Increased sense of humor— A general amplification of one's sensitivity to finding things humorous and amusing, often causing p...
- Introspection— An enhanced state of self-reflective awareness in which one feels drawn to examine their own thought...
- Memory suppression— A dose-dependent inhibition of one's ability to access and utilize short-term and long-term memory, ...
- Motivation suppression— Motivation suppression is a state of diminished drive and willingness to engage in goal-directed beh...
- Novelty enhancement— A feeling of increased fascination, awe, and childlike wonder attributed to everyday concepts, objec...
- Thought acceleration— The experience of thoughts occurring at a dramatically increased rate, as if the mind has been shift...
- Thought deceleration— The experience of thoughts occurring at a markedly reduced pace, as if the mind has been placed into...
- Time distortion— Subjective perception of time becomes dramatically altered — minutes may feel like hours, or hours p...
- Wakefulness— An increased ability to stay awake and alert without the desire to sleep. Distinct from stimulation ...
Multi-sensory(1)
- Scenarios and plots— Scenarios and plots are the narrative structures that emerge within hallucinatory states — coherent ...
Pharmacology
Mechanism of Action
2C-B-FLY's psychedelic effects are produced through agonist activity at serotonin 5-HT2A receptors in the prefrontal cortex — the same primary mechanism shared by all classical phenethylamine psychedelics. Like 2C-B, it acts as a partial agonist, producing submaximal receptor activation with agonist-like intrinsic activity. The bicyclic dihydrofuran "butterfly" structure constrains the methoxy substituents in a fixed spatial orientation that may enhance receptor binding compared to the freely rotating methoxy groups of 2C-B.
Additional Receptor Targets
Beyond 5-HT2A, 2C-B-FLY is likely to share the binding profile breadth characteristic of phenethylamine psychedelics, including agonist activity at 5-HT2B and 5-HT2C receptors. The 5-HT2B activity is notable from a cardiovascular safety standpoint — prolonged 5-HT2B agonism has been linked to cardiac valvulopathy in other contexts. The implications for intermittent recreational use are uncertain but represent a theoretical concern worth acknowledging.
Potency
2C-B-FLY is substantially more potent by weight than 2C-B. This is consistent with the general finding that "butterfly" cyclization of phenethylamine methoxy groups enhances receptor affinity, likely by pre-organizing the methoxy oxygens in the bioactive conformation. This potency difference — perhaps 2–4-fold — means that dosing errors carry greater consequences.
Pharmacokinetics
No formal human pharmacokinetic studies exist. The extended duration compared to 2C-B (5–8 hours vs. 4–6 hours) suggests that the dihydrofuran modification slows metabolic clearance, potentially by reducing the accessibility of the methoxy groups to CYP450-mediated O-demethylation.
Detection Methods
Urine Detection
2C-B-FLY is not specifically targeted by standard immunoassay-based urine drug panels. However, because 2C-x phenethylamines share structural features with amphetamines, they may trigger false positives on amphetamine immunoassays in some cases. The likelihood of cross-reactivity depends on the specific immunoassay manufacturer and the antibody selectivity used. Urine detection windows for 2C-B-FLY are estimated at 24 to 72 hours following ingestion when analyzed by LC-MS/MS methods, though limited pharmacokinetic data exists for many 2C-x compounds.
Blood and Serum Detection
Blood detection windows for 2C-B-FLY are approximately 6 to 24 hours after oral administration. Peak plasma concentrations typically occur 1 to 3 hours post-ingestion. The relatively short half-lives of most 2C-x phenethylamines mean that blood testing must be performed promptly to capture detectable concentrations. LC-MS/MS is the only reliable method for quantitative blood analysis.
Standard Drug Panel Inclusion
2C-B-FLY is NOT specifically included on standard 5-panel, 10-panel, or 12-panel drug screens. The primary concern for individuals undergoing routine screening is the potential for amphetamine cross-reactivity on immunoassay-based panels. If a presumptive positive for amphetamines occurs, confirmatory testing by GC-MS or LC-MS/MS would not confirm amphetamine and the result would be reported as negative unless the laboratory specifically tests for 2C-x compounds. Most routine laboratories do not include 2C-x phenethylamines in their confirmatory panels.
Confirmatory Methods
Definitive identification of 2C-B-FLY requires LC-MS/MS or GC-MS with appropriate reference standards. Some forensic toxicology laboratories include 2C-x phenethylamines in their extended novel psychoactive substance panels. Immunoassay cross-reactivity alone is insufficient for confirmation and would be resolved by standard confirmatory procedures. Quantitative analysis typically requires specific method development as these compounds are not part of routine clinical chemistry workflows.
Reagent Testing (Harm Reduction)
For harm reduction identification, the Marquis reagent is a primary screening tool for 2C-B-FLY. The Marquis reagent produces a green to yellow-green reaction with 2C-B-FLY, distinct from the more common yellow-green of 2C-B. The Mecke reagent may provide additional color reactions that help differentiate between specific 2C-x variants. The Ehrlich reagent shows no reaction with 2C-x phenethylamines, which can help distinguish them from tryptamines and lysergamides. The Mandelin reagent may produce green to brown reactions depending on the specific compound. Using multiple reagents in combination provides the most reliable field identification, though reagent testing cannot determine purity or dosage.
Interactions
| Substance | Status | Note |
|---|---|---|
| 3-FMA | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 4-MMC | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| 8-Chlorotheophylline | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| Adrafinil | Caution | Increases anxiety, cardiovascular stress, and psychological intensity |
| Anandamide | Caution | Cannabis can unpredictably intensify psychedelic effects and increase anxiety |
| Cannabis | Uncertain | — |
| 1,3-Butanediol | Low Risk & Synergy | Cross-tolerance exists; effects compound |
| 25E-NBOH | Low Risk & Synergy | Cross-tolerance exists; effects compound |
| 2C-T | Low Risk & Synergy | Cross-tolerance exists; effects compound |
| 2C-T-2 | Low Risk & Synergy | Cross-tolerance exists; effects compound |
History
Synthesis and Initial Publication
2C-B-FLY was first synthesized by Aaron P. Monte at the University of Montana and was reported in a 1999 paper in the Journal of Medicinal Chemistry as part of a structure-activity relationship study of 2C-B analogs. The research was academic in nature, aimed at understanding the pharmacological basis of psychedelic activity rather than producing a drug of abuse.
Emergence as a Research Chemical
The compound attracted attention in the research chemical community in the mid-2000s as online chemical vendors expanded their offerings beyond the compounds documented in PiHKAL. Its reputation as producing a "smooth" and visually rich experience, combined with its relatively low dosing, made it a point of interest. Community reports accumulated on platforms such as Erowid's Experience Vaults and later on Reddit's psychedelic forums.
Regulatory Status
2C-B-FLY occupies a variable legal status internationally. In the United States it is not explicitly scheduled at the federal level, though the Federal Analogue Act may apply given structural similarity to 2C-B (Schedule I). It is explicitly controlled in several European nations. The patchwork of legal statuses across jurisdictions makes its legal standing uncertain in many regions.
Microdosing Interest
A small community has explored 2C-B-FLY specifically in the context of microdosing — sub-perceptual doses taken on a protocol schedule. This interest appears driven by reports of subtle cognitive enhancement and mood improvement at doses below the threshold of full perceptual effects.
Harm Reduction
Potency Awareness
2C-B-FLY is significantly more potent by weight than 2C-B. If your dose reference point is 2C-B, scale down accordingly. Do not assume a "similar" amount to your 2C-B experiences will produce comparable effects.
Start Very Low
Given the steep dose-response curve and high individual variability, first experiences should begin at 5 mg or below. Community experience suggests that 10–15 mg produces strong effects for most users; doses above 20 mg enter territory with meaningful risk of overwhelming intensity.
Accurate Weighing is Essential
At the active milligram quantities involved, a precision milligram scale capable of resolving 1 mg increments is mandatory. Eyeballing or using a standard scale is not acceptable for a compound active at these doses.
Extended Duration Planning
Allow 8+ hours of unobligated time. The experience may extend significantly longer than expected, particularly if a moderately high dose was taken. Do not have driving, work, or care responsibilities that could conflict with a 6–10 hour experience window.
Sober Sitter for New Users
Given the unpredictable intensity, a trusted, sober person present for a first experience with 2C-B-FLY is strongly recommended.
Dangerous Combinations
Toxicity & Safety
Overview
2C-B-FLY has limited formal toxicological characterization. The available human safety data consists almost entirely of case reports and community experience. While the compound has been used by many thousands of people without reported fatalities, the absence of rigorous safety studies means that meaningful risks remain unquantified.
Cardiovascular Effects
Reports of cardiovascular effects at higher doses are more prominent for 2C-B-FLY than for 2C-B. Tachycardia, hypertension, and general sympathetic activation are expected from the phenethylamine pharmacology. The theoretical 5-HT2B cardiac concern (see pharmacology) is an additional consideration for individuals with pre-existing cardiac conditions.
Steep Dose-Response
A well-documented community observation is that 2C-B-FLY's dose-response curve is steep and individual variability is high. A dose that one person finds mildly stimulating can be intensely psychedelic for another. This unpredictability makes it particularly important to start well below the expected active threshold.
Psychological Risks
Anxiety, panic, and psychological overwhelm are risks common to all potent psychedelics and are relevant for 2C-B-FLY at higher doses. The extended duration (compared to 2C-B) means that a difficult experience will persist longer before natural resolution.
Drug Interactions
Addiction Potential
not habit-forming
Overdose Information
Fatal overdose from 2C-B-FLY alone, at doses within the typical recreational range, is extremely unlikely based on the available evidence for classical psychedelics. The therapeutic index for most psychedelics is very wide.
However, psychological emergencies can occur and require appropriate response:
- Severe anxiety, panic, or psychotic episodes
- Dangerous behavior due to impaired reality testing
- Self-harm in the context of a distressing experience
Emergency management: If someone is experiencing a severe adverse reaction, move them to a calm, quiet environment. Speak reassuringly. Do not restrain unless there is immediate danger. Benzodiazepines (if available and the person is conscious and able to swallow) can reduce acute anxiety. If psychotic symptoms, self-harm risk, or medical distress is present, seek emergency medical attention.
Medical attention: Seek help immediately for seizures, extremely elevated body temperature, signs of serotonin syndrome (agitation, tremor, diarrhea, rapid heart rate), or if the substance consumed is uncertain.
Tolerance
| Full | almost immediately after ingestion |
| Half | 3 days |
| Zero | 7 days |
Cross-tolerances
Legal Status
Regulatory Status
2C-B-FLY (2-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b']difuran-4-yl)ethanamine) occupies a legal grey area in many jurisdictions. It is not specifically listed in international drug control treaties, and its legal status varies significantly between countries depending on how broadly their controlled substance legislation is drafted.
United States
2C-B-FLY is not explicitly scheduled under the Controlled Substances Act. However, theFederal Analogue Act (21 U.S.C. section 813) may apply because 2C-B-FLY is structurally related to 2C-B (Schedule I) --- specifically, it is the dihydrodifuran (restricted-rotation) analogue of 2C-B. Prosecution under the Analogue Act requires evidence of intent for human consumption and a determination that the substance is "substantially similar" in structure or pharmacological effect to a Schedule I compound .
Canada
2C-B-FLY is classified as a Schedule III controlled substance under the Controlled Drugs and Substances Act, effective October 31, 2016. The scheduling captured 2C-B-FLY as a derivative of 2,5-dimethoxyphenethylamine through a comprehensive amendment covering the broader 2C phenethylamine class, including analogues and structural isomers .
United Kingdom
Covered by the Psychoactive Substances Act 2016 (blanket ban on production, supply, and possession with intent to supply of psychoactive substances). May also be prosecutable under theMisuse of Drugs Act 1971 as a phenethylamine analogue.
European Union
Legal status varies by member state. The substance has been monitored by the EMCDDA (European Monitoring Centre for Drugs and Drug Addiction) through the EU Early Warning System since 2007, but no EU-wide scheduling has been enacted. Individual member states includingDenmark andSweden have specifically scheduled it under national legislation.
Other Jurisdictions
- Australia: Likely captured under Schedule 9 analogue provisions.
- Japan: Controlled as a designated substance.
References
21 U.S.C. section 813 --- Federal Analogue Act. Government of Canada. Controlled Drugs and Substances Act, Schedule III, Section 28.
Experience Reports (1)
Tips (3)
Have a trip sitter present, ideally someone with psychedelic experience. They should remain calm and reassuring without being intrusive. A good sitter can make the difference between a challenging experience and a genuine crisis.
Do not combine 2C-B-FLY with lithium (seizure risk), tramadol (seizure/serotonin syndrome risk), or cannabis at higher doses unless very experienced. Cannabis dramatically intensifies and can destabilize a psychedelic experience.
Use a milligram scale to weigh 2C-B-FLY if it comes as a powder. Eyeballing doses of potent psychedelics is irresponsible. A quality 0.001g scale costs under $30 and could prevent a seriously overwhelming experience.
See Also
References (4)
- Psilocybin produces substantial and sustained decreases in depression and anxiety — Griffiths et al. Journal of Psychopharmacology (2016)paper
- Neural correlates of the LSD experience revealed by multimodal neuroimaging — Carhart-Harris et al. PNAS (2016)paper
- 2C-B-FLY - TripSit Factsheet
TripSit factsheet for 2C-B-FLY
tripsit - 2C-B-FLY - Wikipedia
Wikipedia article on 2C-B-FLY
wikipedia