Research chemicalResearch chemicalPhenethylaminePsychedelic

25I-NBF

Also known as NBF-2C-I · 2C-I-NBF

Written by enwyReviewed 5 Aug 20261 sources0 comments

25I-NBF is a potent serotonergic psychedelic, the N-(2-fluorobenzyl) analogue of 2C-I and a close relative of 25I-NBOMe. Active in the low milligram to sub-milligram range and typically taken sublingually or on blotter. Human data is essentially limited to anecdotal reports; the compound is very poorly studied, and its narrow safety margin combined with strong vasoconstriction makes it dangerous.

01 Overview

25I-NBF replaces the N-benzyl methoxy group of the NBOMe series with a fluorine, producing another high-potency 5-HT2A agonist. Like other N-benzyl phenethylamines it is active at very low doses and is difficult to dose accurately on blotter, where it may be mistaken for LSD or NBOMe.

There is almost no formal human pharmacology or toxicology. Given the shared mechanism with the NBOMe class, which has caused severe vasoconstriction, seizures, hyperthermia and deaths, 25I-NBF should be treated as carrying comparable risks. The narrow margin between an active and a harmful dose is the primary hazard, and pronounced vasoconstriction is reported across the family.

02 Mechanism

Potent agonist at serotonin 5-HT2A receptors; the N-2-fluorobenzyl group increases receptor affinity relative to the parent 2C-I.

03 Dosing

Tier	Dose	Route	Notes
Threshold	200–500 mcg	Sublingual	First noticeable effects; sensitivity varies and blotter dosing is imprecise.
Common	500–1500 mcg	Sublingual	Anecdotal range; not clinically validated.
Strong	1500–2500 mcg	Sublingual	Higher doses sharply increase the risk of severe adverse effects.

04 Effects

Effect	Magnitude	Evidence
Visual distortionColour enhancement, patterning and visual movement reported by users.	strong	Anecdotal
Altered mood and cognitionEmotional and cognitive shifts typical of classical psychedelics.		Anecdotal
StimulationPhysical stimulation and restlessness commonly reported with N-benzyl phenethylamines.		Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence
Anxiety and confusionOverwhelming or frightening experiences, especially with unexpected potency.	Moderate	Common	Anecdotal
Peripheral vasoconstrictionMarked vasoconstriction causing cold, painful extremities; the related NBOMe class has caused ischaemic injury.	Severe	Common	Anecdotal
SeizuresConvulsions have been reported across the N-benzyl phenethylamine families after overdose.	Life-threatening	Uncommon but documented in the class	Anecdotal

06 Legal status

United Kingdom

Class A / Psychoactive Substances Act

N-benzyl phenethylamines are controlled. · as of Jan 2026

United States

Possibly controlled as an analogue

May be treated as a controlled substance analogue under the Federal Analogue Act. · as of Jan 2026

07 References

25I-NBF and NBF-series reportsPubMed search

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.