Sunday, 21st October 2018


Fluoromethcathinone (Flephedrone)

Introduction:  Flephedrone is a fluorinated analog of cathinone similar in structure and activity to Mephedrone.

Flephedrone strictly refers to the fluorine atom at position 4 of the ring, however substitution at the 3-position is also reported.  Both isomers have been controlled in the UK as Class B drugs since 16-4-2010. Wikipedia reports “4-Fluoromethcathinone started to be sold over the internet as a designer drug in 2008.  4-FMC has only a short history of human use and its toxicity is not well established


Incidence & Chemistry

Archer[i] identified contents of tablets marketed in the UK as plant feeders in 2009, noting “The material is identified as being 3'-fluoromethcathinone. The compound in the capsule was identified by GC-MS, 1H, (13)C and (19)F NMR as well as FTIR. Other materials identified in the tablet were caffeine and a methylamine salt. The exact position of the fluorine in the fluoromethcathinone was determined by comparison with materials synthesised in our laboratory. Internet-based companies are known to sell 4'-fluoromethcathinone (flephedrone).” Sorenson[ii] developed a protocol for identification and quantitiative testing of cathinone derivatives (inc flephedone) levels in blood samples.


Brandt et al[iii] analysed ‘second generation’ legal highs following the ban on mephedrone on 16-4-10, finding “Overall, the purchased products consisted of single cathinones or cathinone mixtures including mephedrone, butylone, 4-methyl-N-ethylcathinone, flephedrone (4-fluoromethcathinone) and MDPV (3,4-methylenedioxypyrovalerone), respectively. Benzocaine, caffeine, lidocaine, and procaine were also detected. The emphasis was placed on 'Energy 1' (NRG-1), a product advertised as a legal replacement for mephedrone-type derivatives usually claiming to contain naphyrone (naphthylpyrovalerone, O-2482). It was found that 70% of NRG-1 and NRG-2 products appeared to contain a mixture of cathinones banned in April 2010 and rebranded as 'new' legal highs, rather than legal chemicals such as naphyrone as claimed by the retailers. Only one out of 13 NRG-1 samples appeared to show analytical data consistent with naphyrone. These findings also suggest that both consumers and online sellers (unlike manufacturers and wholesalers) are, most likely unknowingly, confronted with the risk of criminalization and potential harm.”  Brandt et al[iv] later noted the presence of different stereoisomers of the drug.   A drug users forum published a batch analysis of NRG1 on 14-6-10[v] finding a roughly even mixture of MDPV and suspected fluorinated cathinone (4-FMC, 3 FMC or 4-FMC, flephedrone)


No respondents to IDMU surveys in 2009/10 listed flephedrone as a drug they had knowingly used using write-in options (other than as NRG1).



A Drug Users forum asks subscribers for reports on their experiences with flephedrone[vi], 10x user reports were noted, dosages ranged from 100-250mg nasally (duration of effects 30min-3hrs), 100-400mg orally (2-4 hrs) and one report of 700mg used rectally (12hrs).



A Drug Users forum asks subscribers for reports on their experiences with flephedrone[vii], Effects were similar to classic stimulants, euphoria, stimulation/energy and mood elevation, focus/productivity and increased libido were reported as positive effects, described by most correspondents as weaker and shorter-lived than with mephedrone.  The most commonly-reported negative effects were comedown and cravings, insomnia, bruxism and lethargy/depression after use.


Karila & Reynaud[viii], investivating the health consequences of cathininone (inc flephedrone) usage, reported “There is evidence that negative health and social consequences may occur in recreational and chronic users. The addictive potential of designer drugs is not weak. Non-fatal overdoses and deaths related to… synthetic cathinones have been reported



Very little is known about the effects of Flephedrone although user reports suggest a stimulant effect milder and of shorter duration than that of Mephedrone, NRG1 or MDPV.  Toxicity and long term effects are unknown.

[i] Archer RP. [2009] Fluoromethcathinone, a new substance of abuse. Forensic Sci Int. 2009 Mar 10;185(1-3):10-20. Epub 2009 Feb 4.

[ii] Sørensen LK. [2011] Determination of cathinones and related ephedrines in forensic whole-blood samples by liquid-chromatography-electrospray tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Feb 13. [Epub ahead of print]

[iii] Brandt SD, Sumnall HR, Measham F, Cole J [2010] Analyses of second-generation 'legal highs' in the UK: initial findings. Drug Test Anal. 2(8):377-82

[iv] Brandt SD, Wootton RC, De Paoli G, Freeman S. [2010] The naphyrone story: The alpha or beta-naphthyl isomer? Drug Test Anal. 2(10):496-502.




[viii] Karila L, Reynaud M. [2010] GHB and synthetic cathinones: clinical effects and potential consequences. Drug Test Anal. 2010 Dec 2. [Epub ahead of print]