4-FA

The 150 mg dose arm of the sole controlled human study was terminated for cardiovascular safety concerns after 5 participants.supported

150 mg arm cancelled after interim safety review due to severe BP elevation. fphar.2018.00713

In the controlled Phase 1 study (100 mg oral, N=12), de Sousa Fernandes Perna and colleagues documented strong blood pressure elevation persisting 4–5 hours post-dose and sustained tachycardia persisting beyond the blood pressure peaksupported

100 mg: strong BP elevation up to 4-5 h, sustained tachycardia. fphar.2018.00713

Gresnigt and colleagues retrospectively compared 4-FA, MDMA, and amphetamine presentations at Dutch emergency departments and found that 4-FA produced exaggerated blood pressure effects compared to both MDMA and amphetaminesupported

Retrospective ED analysis. 4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. emp2.12813

Classic Takotsubo: Toxicologically confirmed 4-FA mono-intoxicationsupported

Case report of Takotsubo cardiomyopathy following 4-FA mono-intoxication, confirmed by toxicological analysis. 15563650.2020.1757695

Reverse-type Takotsubo: Acute heart failure after a single recreational dose in a healthy young individual, confirmed as 4-FA mono-intoxicationsupported

Case report of reverse type Takotsubo cardiomyopathy causing acute heart failure after a single recreational dose of 4-FA in a healthy young individual. Lab confirmed 4-FA mono-intoxication. j.toxrep.2020.12.003

Hondebrink and colleagues prospectively documented fatalities, cerebral hemorrhage, and severe cardiovascular toxicity in a Dutch Poisons Information Centre cohort: 2 fatalities, 4 patients with cerebral hemorrhage (1 fatal), 2 with Takotsubo-type cardiomyopathy, 1 myocardial infarction, and 1 acute heart failure casesupported

Prospective cohort study of adverse health effects after 4-FA use. Documents fatalities, cerebral hemorrhage, and severe cardiovascular toxicity. j.annemergmed.2017.07.482

Wijers and colleagues independently documented two patients with hemorrhagic stroke following 4-FA usesupported

Two patients with severe 4-FA-related complications (hemorrhagic stroke). s00415-018-8888-6

The exaggerated hypertensive response provides a plausible mechanism — severe blood pressure surges rupturing cerebral vasculature.supported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. Documents cardiomyopathy, MI, and cerebral hemorrhage. emp2.12813

Zwartsen and colleagues screened 4-FA in human iPSC-derived cardiomyocytes using microelectrode arrays:supported

Screening of 4-FA and other drugs in hiPSC-derived cardiomyocytes. j.yjmcc.2019.09.007

In SH-SY5Y human neuroblastoma cells, 4-FA depleted cellular ATP with an IC₅₀ of approximately 1.4 mM, decreased mitochondrial membrane potential, and increased reactive oxygen species (ROS) productionsupported

4-FA IC50 for cellular ATP depletion ~1.4 mM in SH-SY5Y cells. Mitochondrial membrane potential decreased. ROS increase. ijms21082841

In cortical MEA cultures, 4-FA inhibited neuronal activity with an IC₅₀ of 113 µM — the least potent of tested NPS (methoxetamine IC₅₀ = 0.5 µM for comparison), suggesting lower acute neurotoxic potential than dissociative NPS.supported

4-FA decreases neuronal activity in cortical cultures on MEA. IC50 of 113 µM for neuronal activity inhibition — least potent of the tested drugs. j.neuro.2016.04.020

In HepG2 human hepatoma cells, 4-FA depleted cellular ATP at 0.25–2 mM and caused membrane integrity loss at ≥0.5 mM, consistent with mitochondrial toxicity in liver cellssupported

Mitochondrial toxicity in HepG2 cells with ATP depletion at 0.25-2 mM. fphar.2019.00438

Mono-intoxication and polydrug fatalities: Hondebrink and colleagues documented fatalities in the Dutch cohort attributable to 4-FA.supported

Documents fatalities, cerebral hemorrhage, and severe cardiovascular toxicity. j.annemergmed.2017.07.482

Combination fatalities: Gerostamoulos and colleagues documented six fatalities over 9 months in Australia from capsules containing premixed 4-FA and 25C-NBOMesupported

Six fatalities from combination of 4-FA and 25C-NBOMe over 9 months. bkac059

Controlled human data document negative affect emergence during the subacute phase following 4-FA administration — a comedown period marked by low mood, irritability, headache, and cognitive fatiguesupported

Negative affect during subacute phase. fphar.2018.00713

Claim in safety — inconclusiveinconclusiveworking →

Given the mild psychedelic state produced at standard doses, precipitation of psychotic episodes in vulnerable individuals (personal or family history of psychotic disorders) is pharmacologically plausible but undocumented for 4-FA specificallysupported

4-FA induced a mild psychedelic state highest at 1h post-dose. 02791072.2019.1569286

4-FA demonstrates moderate abuse liability based on converging evidence: significant increases in drug liking and drug wanting in controlled human studies, positive reinforcement in primate self-administration at fixed-ratio and progressive-ratio schedules, and a DA:5-HT release ratio that preserves more reinforcing efficacy than MDMAsupported

4-FA increases drug liking and wanting (reward/craving measures). s00213-018-4931-7

4-FA demonstrates moderate abuse liability based on converging evidence: significant increases in drug liking and drug wanting in controlled human studies, positive reinforcement in primate self-administration at fixed-ratio and progressive-ratio schedules, and a DA:5-HT release ratio that preserves more reinforcing efficacy than MDMAsupported

All analogs positive reinforcers in rhesus monkeys. Lower 5-HT:DA ratio = higher reinforcing efficacy. pmid:15677348

Psychological dependence potential is moderate, driven by the reward pathway sensitization mechanism documented in the controlled study.supported

4-FA increases drug liking and wanting (reward/craving measures). s00213-018-4931-7

Inan and colleagues conducted a systematic critical review of 4-FA drug interactions with prescription medications, providing the primary evidence base for interaction risk assessment.supported

Reviews drug-drug interactions with antidepressants (SSRIs, MAOIs), ADHD medications, antiretrovirals. ftd.0000000000000725

Six fatalities from 4-FA combined with 25C-NBOMe (a 5-HT₂A agonist) confirmed that dual serotonergic augmentation — transporter-mediated release plus direct receptor agonism — can be fatal at concentrations that are individually survivablesupported

Six fatalities from combination of 4-FA and 25C-NBOMe over 9 months. Both drugs elevate serotonin and act as stimulants. bkac059

MAOIs represent an absolute pharmacological contraindication. 4-FA releases massive monoamine quantities; MAO inhibition prevents catabolism, producing a convergent risk of hypertensive crisis, hyperthermia, and serotonin syndrome.supported

Reviews drug-drug interactions with antidepressants (SSRIs, MAOIs)... Serotonin syndrome risk with serotonergic drugs. ftd.0000000000000725

Combined use may either reduce the entactogenic effects of 4-FA (by blocking the transporter through which 4-FA induces 5-HT release) or, in some regimens, potentiate serotonin syndrome risk.supported

Reviews drug-drug interactions with antidepressants (SSRIs, MAOIs)... Serotonin syndrome risk with serotonergic drugs. ftd.0000000000000725

Claim in safety — inconclusiveinconclusiveworking →

ADHD medications (methylphenidate, amphetamine salts) produce additive cardiovascular effects when combined with 4-FA — additive sympathomimetic stimulation increasing hypertension, tachycardia, and arrhythmia risk.supported

Reviews drug-drug interactions with... ADHD medications... ftd.0000000000000725

Antiretrovirals (particularly ritonavir and other CYP2D6 inhibitors) may reduce 4-FA metabolism, producing elevated plasma concentrations and intensified, prolonged effects.supported

Reviews drug-drug interactions with... antiretrovirals... CYP enzyme interactions. ftd.0000000000000725

Cardiovascular disease and uncontrolled hypertension represent absolute clinical contraindications based on the documented pronounced and prolonged blood pressure elevation and the occurrence of Takotsubo cardiomyopathy, myocardial infarction, and hemorrhagic stroke in the clinical record.supported

100 mg: strong BP elevation up to 4-5 h, sustained tachycardia. 150 mg arm cancelled after interim safety review due to severe BP elevation. fphar.2018.00713

Cardiovascular disease and uncontrolled hypertension represent absolute clinical contraindications based on the documented pronounced and prolonged blood pressure elevation and the occurrence of Takotsubo cardiomyopathy, myocardial infarction, and hemorrhagic stroke in the clinical record.supported

Documents cardiomyopathy, MI, and cerebral hemorrhage. emp2.12813

Concurrent MAOI use is an absolute pharmacological contraindication due to the risk of hypertensive crisis and serotonin syndrome from uninhibited monoamine accumulation.supported

Reviews drug-drug interactions with antidepressants (SSRIs, MAOIs)... Serotonin syndrome risk with serotonergic drugs. ftd.0000000000000725

Concurrent serotonergic drug use (SSRIs, SNRIs, tramadol, serotonergic psychedelics) is a relative-to-absolute contraindication depending on the specific agent, with documented fatality risk for the combination with 25C-NBOMe.supported

Six fatalities from combination of 4-FA and 25C-NBOMe over 9 months. bkac059

Patients on antiretroviral therapy involving CYP2D6 inhibitors face pharmacokinetic risk of intensified 4-FA effects.supported

Reviews drug-drug interactions with... antiretrovirals... CYP enzyme interactions. ftd.0000000000000725

Urinary excretion and metabolic pathway analysis was performed in 12 subjects (100 mg) and 5 subjects (150 mg)supported

12 subjects ingested 100 mg, 5 subjects 150 mg 4-FA. j.jpba.2019.113008

Urine concentrations ranged 0.7–38 mg/L, with creatinine-normalized excretion peaking at approximately 4 hours post-ingestion.supported

Urine concentrations 0.7-38 mg/l. Creatinine-normalized peak at 4h post-ingestion. j.jpba.2019.113008

Rickli and colleagues characterized the transporter interaction profile of 4-FA alongside other para-halogenated amphetamines in HEK293 cells expressing human transporterssupported

Evaluated transporter and receptor interaction profiles of para-substituted amphetamines. 4-FA releases NE, DA, and 5-HT similarly to MDMA. j.euroneuro.2014.12.012

Luethi and colleagues independently confirmed these transporter interactions, demonstrating NET inhibition at submicromolar concentrations and DAT inhibition at low micromolar concentrations, with the para-fluorine increasing SERT inhibition potency relative to amphetamine (though less potently than para-chlorine substitution).supported

Para-fluoroamphetamine inhibits NET at submicromolar concentrations, DAT at low micromolar. Fluorine substituent reduces DAT:SERT selectivity vs unhalogenated amphetamine. Toxicity rank: Cl > F > H. fphar.2019.00438

Quantitative releasing potencies were characterized in rat brain synaptosomes by Baumann and colleagues: all para-substituted amphetamine analogs exhibited DA release EC₅₀ values in the 24–52 nM rangesupported

p-Fluoroamphetamine: DA EC50 ~44 nM in vitro. jpet.110.176271

Wee and colleagues specifically measured 4-FA (designated PAL 303) 5-HT release EC₅₀ at 939 nM, compared to DA release EC₅₀ in the same 24–52 nM rangesupported

PAL 303 (para-fluoroamphetamine): 5-HT release EC50 = 939 nM. pmid:15677348

Beyond transporter-mediated release, 4-FA exhibits affinity for the 5-HT₂A receptor, consistent with the mild psychedelic state observed in controlled human studiessupported

Also has affinity for 5-HT2A receptor. j.euroneuro.2014.12.012

Claim in pharmacology — inconclusiveinconclusiveworking →

Claim in pharmacology — inconclusiveinconclusiveworking →

Baumann and colleagues demonstrated in rat nucleus accumbens microdialysis that para-substituted amphetamine analogs produce dose-related increases in extracellular DA and 5-HTsupported

In vivo: elevated dialysate DA and 5-HT in rat nucleus accumbens. jpet.110.176271

Toennes and colleagues conducted the primary controlled human pharmacokinetic study, characterizing 4-FA in serum and oral fluid after oral ingestion of 100 mg and 150 mg dosessupported

Controlled study evaluating pharmacokinetic parameters of 4-FA in humans after oral ingestion. Serum and oral fluid analysis. dta.2595

By analogy with amphetamine, CYP2D6 involvement is pharmacologically plausible, and Inan and colleagues identified CYP2D6 inhibition by antiretrovirals as a specific interaction risk for 4-FAsupported

Reviews drug-drug interactions with... antiretrovirals... CYP enzyme interactions. ftd.0000000000000725

Claim in pharmacology — inconclusiveinconclusiveworking →

The disproportionate cardiovascular toxicity of 4-FA relative to other stimulants has a clear neurochemical basissupported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. Documents cardiomyopathy, MI, and cerebral hemorrhage. emp2.12813

Why does 4-FA produce greater blood pressure elevation than both MDMA and amphetamine? The comparative cardiovascular toxicity documented by Gresnigt and colleagues is not fully explained by 4-FA's NE releasing potency alone, which is comparable to amphetamine. An additional vasoconstrictive mechanism (direct alpha-1-adrenergic agonism, endothelin pathway activation, or reduced endothelial NO production) may be involved but has not been investigated.supported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. emp2.12813

Baumann and colleagues confirmed dose-dependent DA elevation in rat NAc dialysate following administration of para-substituted amphetamine analogssupported

In vivo: elevated dialysate DA and 5-HT in rat nucleus accumbens. jpet.110.176271

This DA surge in the NAc is the neurochemical substrate for the increased drug liking and drug wanting documented in the controlled human study, and explains 4-FA's behavioral reinforcing efficacy in primate self-administration paradigms.supported

All analogs positive reinforcers in rhesus monkeys. Lower 5-HT:DA ratio = higher reinforcing efficacy. pmid:15677348

Prefrontal cortex DA elevation likely underlies the attention and motor performance improvements observed at peak effect.supported

Peak mood effects at 1h: vigor, friendliness, elation, arousal, positive mood, improved attention/motor performance. fphar.2018.00713

Dampened stimulant locomotion: In vivo microdialysis studies demonstrate that para-substituted amphetamines with greater 5-HT releasing activity produce less forward locomotion than purely catecholaminergic analogs. 5-HT₁B receptor-mediated inhibition of DA neuron firing in the VTA provides a plausible circuit-level mechanismsupported

Serotonin release dampens locomotor stimulant effects. jpet.110.176271

Entactogenic and psychedelic features: The 5-HT₂A receptor affinity combined with synaptic 5-HT elevation is consistent with the mild psychedelic state quantified by Kuypers and colleaguessupported

4-FA induced a mild psychedelic state highest at 1h post-dose. 02791072.2019.1569286

Massive NE release produces sustained sympathetic activation — prolonged hypertension and tachycardia lasting 4–5 hourssupported

100 mg: strong BP elevation up to 4-5 h, sustained tachycardia. fphar.2018.00713

The catecholamine surge is the established mechanism for Takotsubo (stress) cardiomyopathy, and sustained severe hypertension provides a plausible mechanism for the hemorrhagic strokes documented in Dutch case series.supported

Case report of reverse type Takotsubo cardiomyopathy causing acute heart failure after a single recreational dose of 4-FA in a healthy young individual. j.toxrep.2020.12.003

The catecholamine surge is the established mechanism for Takotsubo (stress) cardiomyopathy, and sustained severe hypertension provides a plausible mechanism for the hemorrhagic strokes documented in Dutch case series.supported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. Documents cardiomyopathy, MI, and cerebral hemorrhage. emp2.12813

The demonstration that serotonergic activity inversely correlates with stimulant locomotion in para-substituted amphetamines reflects a broader pharmacological principle: 5-HT release in the mesolimbic pathway attenuates the reinforcing efficacy of concurrent DA releasesupported

Serotonin release dampens locomotor stimulant effects. p-FA is potent at both DA and 5-HT releasing. jpet.110.176271

The Takotsubo cardiomyopathy cases are understood through the catecholamine cardiotoxicity model: supraphysiological NE and epinephrine concentrations activate beta-1-adrenergic receptors on cardiomyocytes, producing calcium overload, oxidative stress, and transient contractile dysfunction (myocardial "stunning")supported

Case report of Takotsubo cardiomyopathy following 4-FA mono-intoxication, confirmed by toxicological analysis. 15563650.2020.1757695

Synthesized no later than the 1940s as a pharmacological tool compound, 4-FA remained obscure until its emergence on the Dutch research chemical market circa 2007partially supported

Investigated temporal pattern of 4-FA appearance on Dutch drug market and patterns of use and effects. add.12932

Following documentation of fatalities and cerebral hemorrhages, 4-FA was progressively scheduled internationally — most recently as a US federal Schedule I substance effective February 2026.partially supported

Prospective cohort study of adverse health effects after 4-FA use. Documents fatalities, cerebral hemorrhage, and severe cardiovascular toxicity. j.annemergmed.2017.07.482

Dopamine release EC₅₀ falls in the 24–52 nM range, while serotonin release EC₅₀ is approximately 939 nM — meaningfully serotonergic but considerably less potent than MDMA at SERTpartially supported

p-Fluoroamphetamine: DA EC50 ~44 nM, 5-HT EC50 ~53 nM in vitro. jpet.110.176271

Dopamine release EC₅₀ falls in the 24–52 nM range, while serotonin release EC₅₀ is approximately 939 nM — meaningfully serotonergic but considerably less potent than MDMA at SERTsupported

PAL 303 (para-fluoroamphetamine): 5-HT release EC50 = 939 nM. pmid:15677348

The para-fluorine substitution reduces DAT:SERT selectivity relative to unsubstituted amphetamine and confers 5-HT₂A receptor affinity.supported

Para-fluoroamphetamine has enhanced serotonergic properties vs amphetamine. Also has affinity for 5-HT2A receptor. j.euroneuro.2014.12.012

Controlled studies confirm a subjective profile combining stimulant activation (vigor, arousal, enhanced attention) with a mild psychedelic and entactogenic state intermediate between amphetamine and MDMAsupported

4-FA induced a mild psychedelic state highest at 1h post-dose. Effects intermediate between amphetamine and MDMA. 02791072.2019.1569286

Peripheral oxytocin concentrations rise independently of empathy measures, and cognitive empathy is paradoxically reducedsupported

4-FA increases peripheral oxytocin concentrations independent of behavioral effects. Reduces cognitive empathy (unlike MDMA). hup.2680

4-FA carries disproportionate cardiovascular risk: blood pressure elevation exceeds that of both MDMA and amphetamine at emergency department presentation, the 150 mg arm of the sole controlled study was terminated for cardiovascular toxicity, and clinical outcomes include Takotsubo cardiomyopathy, hemorrhagic stroke, and fatalitiessupported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. Documents cardiomyopathy, MI, and cerebral hemorrhage. emp2.12813

4-FA carries disproportionate cardiovascular risk: blood pressure elevation exceeds that of both MDMA and amphetamine at emergency department presentation, the 150 mg arm of the sole controlled study was terminated for cardiovascular toxicity, and clinical outcomes include Takotsubo cardiomyopathy, hemorrhagic stroke, and fatalitiessupported

150 mg arm cancelled after interim safety review due to severe BP elevation. 100 mg: strong BP elevation up to 4-5 h, sustained tachycardia. fphar.2018.00713

Six documented deaths from 4-FA combined with 25C-NBOMe confirm lethal serotonergic interaction potentialsupported

Six fatalities from combination of 4-FA and 25C-NBOMe over 9 months. Both drugs elevate serotonin and act as stimulants. bkac059

The toxicological rank order follows the serotonergic potency rank: para-chloroamphetamine (4-CA) is a known serotonergic neurotoxin, while 4-FA's lower serotonergic potency corresponds to lower mitochondrial and hepatocellular toxicity (cytotoxicity rank: Cl > F > H).supported

Toxicity rank: Cl > F > H for para-substituents. ijms21082841

The toxicological rank order follows the serotonergic potency rank: para-chloroamphetamine (4-CA) is a known serotonergic neurotoxin, while 4-FA's lower serotonergic potency corresponds to lower mitochondrial and hepatocellular toxicity (cytotoxicity rank: Cl > F > H).supported

Toxicity rank: Cl > F > H. fphar.2019.00438

Cardiovascular toxicity: 4-FA produces exaggerated blood pressure effects compared to amphetamine at emergency department presentation, a clinically important distinction for risk assessment.supported

4-FA produces exaggerated blood pressure effects vs MDMA and amphetamine. emp2.12813

Luethi demonstrated that in vitro monoamine transporter and receptor interaction profiles predict reported human active doses across a range of novel psychoactive stimulants and psychedelics. 4-FA's transporter profile contextualizes its active dose range (100–150 mg oral) relative to its in vitro potency, supporting the general framework that compounds with lower transporter potency require higher doses to produce equivalent subjective effects.supported

In vitro pharmacological profiles of NPS predict psychoactive doses in humans. Transporter potency ratios used to predict active dose ranges. pyy047

Para-halogenation progressively increases SERT interaction potency (Cl > F > H) while maintaining similar catecholaminergic releasing activity across the series (DA release EC₅₀: 24–52 nM range for all analogs).supported

Fluorine substituent reduces DAT:SERT selectivity vs unhalogenated amphetamine. Toxicity rank: Cl > F > H. fphar.2019.00438

Serotonergic activity: 4-FA exhibits meaningfully higher SERT releasing activity (5-HT EC₅₀ = 939 nM) compared to amphetamine (minimal SERT activity). This serotonergic component confers entactogenic and mild psychedelic properties absent from the amphetamine experience.supported

PAL 303 (para-fluoroamphetamine): 5-HT release EC50 = 939 nM. pmid:15677348

The comparative cardiovascular finding is clinically critical: users who perceive 4-FA as "ecstasy light" (a common market framing) may underestimate cardiovascular risk, which is in fact greater with 4-FA than with MDMA.supported

Investigated temporal pattern of 4-FA appearance on Dutch drug market and patterns of use and effects. add.12932

The Poisons Information Centre documented increasing intoxication presentations, and by 2018 Hondebrink and colleagues published a prospective cohort documenting fatalities, cerebral hemorrhages, and severe cardiovascular toxicity directly attributable to 4-FAsupported

Combined drug market data with Poisons Information Centre intoxication data. 4-FA among top NPS. j.drugalcdep.2014.11.033

The Poisons Information Centre documented increasing intoxication presentations, and by 2018 Hondebrink and colleagues published a prospective cohort documenting fatalities, cerebral hemorrhages, and severe cardiovascular toxicity directly attributable to 4-FAsupported

Prospective cohort study of adverse health effects after 4-FA use. Documents fatalities, cerebral hemorrhage, and severe cardiovascular toxicity. j.annemergmed.2017.07.482

Studies were conducted as investigator-initiated Phase 1 pharmacology research in healthy poly-drug users receiving 100 mg oral 4-FA; a planned 150 mg arm was terminated for cardiovascular safety concernssupported

Phase 1, placebo-controlled within-subject trial in N=12. 100 mg arm completed; 150 mg arm cancelled after interim safety review due to severe BP elevation. fphar.2018.00713

The first detailed in vitro characterization of 4-FA's monoamine-releasing properties in the context of abuse liability appeared in 2005, when Wee and colleagues evaluated it (designated PAL 303) in a series of amphetamine analogs examining the relationship between serotonergic activity and reinforcing effects.supported

PAL 303 (para-fluoroamphetamine): 5-HT release EC50 = 939 nM. All analogs positive reinforcers in rhesus monkeys. pmid:15677348

Unlike most new psychoactive substances, which cycle through markets rapidly, 4-FA exhibited sustained popularity — Linsen and colleagues documented this unusual longevity and the compound's specific market niche as "ecstasy light," a stimulant perceived by users as combining the desirable features of amphetamine and MDMA with reduced adverse effectssupported

Shows sustained use patterns and prevalence. add.12932

Purity and market data from Dutch online and offline drug markets contextualized 4-FA's position as an established commodity rather than a transient novelty.supported

Comparison of online vs offline drug purity in the Netherlands. 4-FA mentioned in context of Dutch drug market analysis. add.13720

Kuypers and colleagues demonstrated that 4-FA (100 mg oral) produces a quantifiable psychedelic state using validated assessment scalessupported

4-FA induced a mild psychedelic state highest at 1h post-dose. Psychedelic state decreased with decreasing serum concentrations. 02791072.2019.1569286

Dolder and colleagues examined the entactogenic properties of 4-FA at 100 mg oralsupported

4-FA increases peripheral oxytocin concentrations independent of behavioral effects. Reduces cognitive empathy (unlike MDMA). Effects intermediate between MDMA and amphetamine on empathy domain. hup.2680

Serum and oral fluid PK (2019): Characterized concentration-time profiles after 100 mg and 150 mg oral dosessupported

Controlled study evaluating pharmacokinetic parameters of 4-FA in humans after oral ingestion. Serum and oral fluid analysis. dta.2595

De Sousa Fernandes Perna and colleagues conducted the first controlled human safety study of 4-FAsupported

Phase 1, placebo-controlled within-subject trial in N=12. fphar.2018.00713

Urinary excretion (2020): Metabolic pathway identification and excretion kinetics in 17 subjectssupported

12 subjects ingested 100 mg, 5 subjects 150 mg 4-FA. Two metabolic pathways identified. j.jpba.2019.113008

The sole published human pharmacokinetic study was conducted by Toennes and colleagues, characterizing 4-FA concentrations in serum and oral fluid after controlled oral ingestion of 100 mg and 150 mg.supported

Controlled study evaluating pharmacokinetic parameters of 4-FA in humans after oral ingestion. Serum and oral fluid analysis. dta.2595

Urine: Peak excretion at ~4 hours; total detection window not precisely characterized beyond the 12-hour study follow-upsupported

Creatinine-normalized peak at 4h post-ingestion. j.jpba.2019.113008

Hair: Detected in postmortem hair samples in a 13-year retrospective forensic studysupported

4-FA among most frequently detected NPS in 1203 postmortem hair samples from 2008-2020. dta.3150

Two primary Phase I metabolic routes were identified from urinary metabolite analysis in 17 subjects:supported

12 subjects ingested 100 mg, 5 subjects 150 mg 4-FA... Two metabolic pathways identified. j.jpba.2019.113008

CYP2D6 involvement is pharmacologically plausible by analogy with amphetamine metabolism, and Inan and colleagues identified CYP2D6 inhibition by antiretroviral drugs as a specific drug interaction risk for 4-FAsupported

Reviews drug-drug interactions with... antiretrovirals... CYP enzyme interactions. ftd.0000000000000725

Rickli and colleagues demonstrated that 4-FA releases NE and DA with potency comparable to amphetamine while releasing 5-HT in a range approaching MDMA in HEK293 cells expressing human transporterssupported

4-FA releases NE, DA, and 5-HT similarly to MDMA. Para-fluoroamphetamine has enhanced serotonergic properties vs amphetamine. j.euroneuro.2014.12.012

The para-fluorine substitution increases SERT inhibition potency relative to unsubstituted amphetamine but less so than para-chlorine substitution — establishing the rank order Cl > F > H for serotonergic potentiation within the para-halogenated amphetamine series.supported

Fluorine substituent reduces DAT:SERT selectivity vs unhalogenated amphetamine. Toxicity rank: Cl > F > H. fphar.2019.00438

This receptor interaction is consistent with the mild psychedelic state quantified in controlled human studies and distinguishes 4-FA from unsubstituted amphetamine.supported

4-FA induced a mild psychedelic state highest at 1h post-dose. Effects intermediate between amphetamine and MDMA. 02791072.2019.1569286

Claim in receptor-pharmacology — inconclusiveinconclusiveworking →

An important interpretive caveat: the characterization that 4-FA releases 5-HT 'similarly to MDMA' appears to conflict with the measured 5-HT release EC₅₀ of 939 nM, which is substantially weaker than MDMA's serotonergic potencysupported

4-FA releases NE, DA, and 5-HT similarly to MDMA. j.euroneuro.2014.12.012

In dance or festival environments, the stimulant dimension dominates (energy, arousal, motor drive); in intimate social settings, the empathogenic warmth and emotional openness become more prominentsupported

Investigated temporal pattern of 4-FA appearance on Dutch drug market and patterns of use and effects. add.12932

Unlike MDMA, cognitive empathy is paradoxically reduced during 4-FA intoxication despite elevated oxytocin, producing an entactogenic state that feels warm and sociable but lacks the deep interpersonal attunement associated with MDMA.supported

4-FA increases peripheral oxytocin concentrations independent of behavioral effects. Reduces cognitive empathy (unlike MDMA). Effects intermediate between MDMA and amphetamine on empathy domain. hup.2680

This structural modification is pharmacologically significant: para-halogenation progressively increases serotonergic potency relative to unsubstituted amphetamine, with the rank order Cl > F > H for SERT inhibitionsupported

Fluorine substituent reduces DAT:SERT selectivity vs unhalogenated amphetamine. Toxicity rank: Cl > F > H. fphar.2019.00438