Research chemicalResearch chemicalBenzodiazepine analogueDepressant

Fonazepam (3-Fluorophenazepam)

Also known as 3-Fluorophenazepam · 3-FPM benzodiazepine (not the stimulant)

Written by enwyReviewed 4 Aug 20261 sources0 comments

Fonazepam, also known as 3-fluorophenazepam, is a designer benzodiazepine structurally derived from phenazepam. It is sold as a research chemical and reported to be long-acting and potent, producing sedation, anxiolysis and amnesia. No clinical human data exists; information is limited to analytical characterisation and user reports.

01 Overview

Fonazepam is a fluorinated analogue of phenazepam that appeared on the research-chemical market as a long-duration sedative. It is typically encountered as powder or in pellets and blotters, and shares the high per-milligram potency characteristic of 2'-halophenazepam derivatives.

User reports describe strong sedation, anxiolysis, muscle relaxation and pronounced amnesia, with effects and impairment persisting well into the following day. Its long half-life makes accumulation with repeated dosing a particular hazard. It has not been studied in humans in a clinical setting.

02 Mechanism

Positive allosteric modulation of GABA-A receptors at the benzodiazepine binding site, potentiating GABAergic inhibition.

03 Dosing

Tier	Dose	Route	Notes
Light	0.1–0.3 mg	Oral	Volumetric dosing recommended due to high potency.
Common	0.3–0.7 mg	Oral	Long duration; carryover into the next day is common.

04 Effects

Effect	Magnitude	Evidence
AnxiolysisReduction of anxiety consistent with the benzodiazepine class.	Marked	Anecdotal
SedationPronounced and long-lasting drowsiness.	Strong	Anecdotal
AmnesiaImpaired memory formation, especially at higher doses.		Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence
Dependence and withdrawalPhysical dependence develops with regular use; abrupt cessation risks rebound anxiety and seizures.	Severe	Common with regular use	Anecdotal
BlackoutsBlackout episodes and amnesia, worsened by alcohol.	Moderate	Common at higher doses	Anecdotal
Additive respiratory depressionDangerous when combined with opioids or alcohol.	Life-threatening	With CNS depressants	Observational

06 Legal status

United States

Not federally scheduled

as of Jan 2026

United Kingdom

Class C

as of Jan 2026

07 References

Designer benzodiazepines: an analytical reviewDrug Testing and Analysis

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.