Research chemicalResearch chemicalPhenethylaminePsychedelicN-benzyl (NBOMe)5-HT2A agonist

25B-NBOMe

Also known as 2C-B-NBOMe · Cimbi-36 · 25B

Written by enwyReviewed 5 Aug 20262 sources0 comments

25B-NBOMe is an N-benzyl phenethylamine psychedelic, the 25-NB derivative of 2C-B. It is an extremely potent serotonin 5-HT2A agonist active in the low-hundred-microgram range. Sold on blotter and frequently misrepresented as LSD, it carries a narrow safety margin, marked vasoconstriction and a documented history of hospitalisations and fatalities.

01 Overview

25B-NBOMe (2C-B-NBOMe) is one of the original NBOMe series compounds characterised by David Nichols' group as radioligands for imaging 5-HT2A receptors. It reached recreational markets around 2010-2013 as blotter and liquid, exploiting its LSD-like potency and appearance.

Human data are limited to case reports and forensic series. Because active doses are measured in micrograms and the dose-response curve is steep, small volumetric or blotter-loading errors can cause severe toxicity: agitation, hyperthermia, seizures, rhabdomyolysis and cardiovascular collapse. Multiple deaths have been attributed to 25B-NBOMe alone or in mixtures.

02 Mechanism

High-affinity, high-efficacy agonist at serotonin 5-HT2A receptors; the N-(2-methoxybenzyl) group dramatically increases 5-HT2A affinity relative to the parent 2C-B. Peripheral 5-HT2A activation drives vasoconstriction.

03 Dosing

Tier	Dose	Route	Notes
Threshold	100–250 µg	Sublingual	Held under tongue; swallowing largely inactivates it.
Common	250–800 µg	Sublingual	Narrow margin; blotter loading is often uneven.
Strong	800–1500 µg	Sublingual	Toxicity risk rises steeply above ~1 mg.

04 Effects

Effect	Magnitude	Evidence
Visual and psychedelic effectsOpen- and closed-eye visuals, colour enhancement and altered thought, LSD-like but often described as more stimulating and less warm.	6-10 h	Anecdotal
StimulationPronounced body stimulation, jaw tension and restlessness, contributing to insomnia and difficulty sitting still.	marked	Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Peripheral vasoconstrictionCold, painful extremities from intense vasoconstriction; case reports of ischaemia.	Severe	Common	Anecdotal
Seizures and hyperthermiaOverdose produces agitation, tachycardia, seizures, hyperthermia and rhabdomyolysis; deaths reported.	Life-threatening	Uncommon but characteristic	Observational

06 Legal status

Germany

NpSG

Covered by the New Psychoactive Substances Act. · as of Jan 2026

United Kingdom

Class A (Misuse of Drugs Act)

NBOMe series controlled as Class A. · as of Jan 2026

United States

Schedule I

NBOMe compounds placed in Schedule I; also captured by the Federal Analogue Act. · as of Jan 2026

07 References

Acute toxicity associated with NBOMe compounds: analytically confirmed casesClinical Toxicology, 2015

EMCDDA report on the risk assessment of 25B-NBOMe class NPSEMCDDA

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.