4-Fluoroamphetamine

Usage

4-FA was popular in the Netherlands where it was predominantly used for its specific effects (77% of users) rather than its legal status (18%). 4-FA has become illegal since May 2017. Since the ban usage has decreased a lot. Accurate statistics of usage are not available until 2020, but submitted samples to get tested were counted. In 2016 1.100 (10%) of samples tested for DIMS were 4-FA samples, in 2024 less than 50 4-FA samples were submitted. In 2020 0,3% of Dutch adults used 4-FA in the previous year, in 2024 this was just 0,1%.

Effects

The subjective effects of 4-fluoroamphetamine include euphoria which some find similar to the effects of MDMA and amphetamine, increased energy (stimulation), mood elevation, feelings of warmth and empathy, excessive talking, bruxism, and suppressed appetite (anorexic). The general course of effects involves primarily empathogenic effects for the first few hours, which fades out as increased stimulation develops over the next several hours.

The dopamine reuptake inhibition produced by 4-FA is stronger than that of either 4-CA or 4-IA. 4-FA also produces less hyperthermia than similar compounds such as PMA, 4-MTA and 4-methylamphetamine.

4-FA has been described as producing a very mild "psychedelic" state, intermediate between that of amphetamine and MDMA. It is unclear whether this is related to induction of monoamine release or serotonin 5-HT2A receptor agonism.

Common acute side effects are nausea, headaches, increased heart rate and insomnia.

Chemistry

4-FA reacts with reagent testing to give a semi-unique array of colors which can be used to aid its identification.

Pharmacology

4-Fluoroamphetamine is a releasing agent and reuptake inhibitor of dopamine, serotonin, and norepinephrine. The respective EC50 values are 200 nM, 730 nM, and 37 nM, while the IC50 values are 770 nM, 6800 nM, and 420 nM.

The drug shows some affinity for the serotonin 5-HT2A receptor (Ki = 11,300nM) and serotonin 5-HT2C receptor (Ki = 7,800nM), similar to that of MDMA in the case of the serotonin 5-HT2A receptor (Ki = 5,900nM), but far below the affinity of structurally related classical serotonergic psychedelics like 2C-B. It has also been shown to act as a very low-potency serotonin 5-HT2B receptor partial agonist ( = 14,400nM; = 58%).

4-Fluoroamphetamine has been found to be a weak monoamine oxidase A (MAO-A) inhibitor, with an of 16,000nM. For comparison, the of amphetamine for MAO-A inhibition was 11,000nM.

Regarding the metabolic fate of 4-FA, the C-F bond at the 4-position on the phenyl ring likely resists deactivation in the liver by cytochrome P450 oxidase.

Neurotoxicity

4-FA does not cause long-lasting depletion of brain serotonin, unlike its analogs 4-CA and 4-BA. This is thought to "reflect the inability of the fluoro-compound to be metabolized in the same way as the other haloamphetamines."

Neurotoxicity does not increase down the series of para-halogenated amphetamine derivatives, even though serotonin releasing potency does follow this trend. For example, 4-iodoamphetamine is less toxic than is 4-chloroamphetamine. Hence, this property is not related to serotonin releasing potency as such, since PAL-287 was reported to be not at all neurotoxic even though it is a powerful 5-HT releasing agent. It is unclear where 4-methylamphetamine fits in on the neurotoxicity scale. The extensive serotonergic neurotoxicity of 4-chloroamphetamine (and its brominated derivative), and the increased serotonergic toxicity of 4-methylamphetamine suggest that para-substitution seems to increase overall serotonergic (neuro)toxicity, compared to amphetamine. Exceptions include 4-MTA, a para-substituted, non-neurotoxic amphetamine.

Toxicology

The LD50 (mouse; i.p.) of 4-FA is 46 mg/kg.

Fluoroamphetamine (isomer not determined) in a capsule mixed with 25C-NBOMe was associated with three deaths in Melbourne in 2017.

Legal status

As of October 2015, 4-FA is a controlled substance in China. 4-FA is banned in the Czech Republic. As of 25 May 2017 4-FA is a controlled substance in the Netherlands. 4-FA is also controlled in Australia, Belgium, UK, Germany, Israel, Slovakia, Bulgaria, Chile, Brazil, Canada, Croatia, Sweden, New Zealand and France.

4-FA is a controlled substance as of 27 August 2014 in South Korea.

Finland

Scheduled in the "government decree on narcotic substances, preparations and plants" and is therefore illegal.

United States

In the United States, on June 3, 2025 the DEA announced by federal register its intent to place 4-Fluoroamphetamine into Schedule I status with public comments closing on July 3, 2025. On January 15, 2026 the DEA placed 4-FA in Schedule 1 of the Controlled Substances Act effective February 17, 2026.

References

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