4-Fluoromethamphetamine (4-FMA)
4-FMA (para-fluoromethamphetamine) is a ring-fluorinated methamphetamine analogue that has appeared on research-chemical markets. The para-fluoro substitution tends to add serotonergic character to fluoroamphetamines, raising concern for serotonin toxicity in addition to standard stimulant risks. Human data is minimal.
01 Overview
4-Fluoromethamphetamine is the para-fluoro N-methyl amphetamine, structurally between methamphetamine and the more serotonergic 4-fluoroamphetamine. It has circulated as a designer stimulant, sometimes mis-sold.
There are no clinical studies. As para-fluorinated phenethylamines can shift activity toward serotonin release, 4-FMA is regarded as carrying both classic sympathomimetic risk and potential serotonin-syndrome risk, particularly with serotonergic co-drugs.
02 Mechanism
Releases/inhibits reuptake of norepinephrine and dopamine with a relatively greater serotonergic component conferred by the para-fluoro group.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Common (approximate, anecdotal) | 20–60 mg | Oral | User-reported; unvalidated. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Stimulation and mood liftEnergy, sociability and euphoria reported. | Moderate | Anecdotal | |
| Empathogenic tingeSome users note mild MDMA-like warmth from the serotonergic component. | Mild | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Cardiovascular strainTachycardia and hypertension. | Moderate | Common | Anecdotal | |
| Serotonin toxicity riskPara-fluoro serotonergic activity raises theoretical risk of serotonin syndrome, especially with MAOIs/SSRIs. | Severe | Unknown; elevated with serotonergic drugs | Unconfirmed |