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Desmethylflunitrazepam

Desmethylflunitrazepam molecule structureDesmethylflunitrazepam molecule structure
Desmethylflunitrazepam
Norflunitrazepam, Fonazepam, Ro05-4435, N-desmethylflunitrazepam

Desmethylflunitrazepam is a benzodiazepine that occurs naturally as a metabolite of flunitrazepamcitation needed and has been distributed as a designer drug and research chemical.1 It acts on the GABAA receptor, producing sedative, anxiolytic, and muscle relaxant effects typical of its class.citation needed As an understudied research chemical derived from a notably potent parent compound, its safety profile and long-term risks remain poorly characterized.

Dosage & Duration

Dosage

Doses are population estimates that vary widely between individuals.

Threshold~0.5 mg
Light0.5-1 mg
Moderate1-2 mg
Strong2-4 mg
Heavy4+ mg

Duration

Onset30-60 minutes
After Effects2-12 hours
Total5-10 hours

Subjective Effects

Legacy content. A statistically backed ontology from Mindstate Design Labs is coming soon.

Desmethylflunitrazepam produces a classic benzodiazepine experience dominated by heavy sedation, anxiety relief, and physical relaxation, consistent with its role as an active metabolite of flunitrazepam. Little formal documentation of its subjective character exists, as it has circulated primarily as a designer benzodiazepine sold online. Memory of the period following ingestion is often unreliable at moderate to high doses.

Physical

Pronounced sedation and muscle relaxation give the body a heavy, tranquil feeling that can progress into sleep at higher doses.

Sedation

Cognitive

The headspace is one of dulled, slowed thought and reduced anxiety, with anterograde amnesia becoming increasingly prominent as the dose rises.

Pharmacology

Pharmacodynamics

Desmethylflunitrazepam is a benzodiazepine that acts as a positive allosteric modulator at the GABA-A receptorcitation needed, where it displays high affinity with an IC50 of 1.499 nM. It is also a metabolite of flunitrazepam.23

Pharmacokinetics

The metabolism of desmethylflunitrazepam (fonazepam) has been characterised in human liver microsomes. Desmethylflunitrazepam underwent monohydroxylation and reduction of the nitro function.citation needed

Interactions

Dangerous

Highest risk

These combinations are considered extremely harmful and should always be avoided. Reactions to these drugs taken in combination are highly unpredictable and have a potential to cause death.

AlcoholGHB/GBLOpioidsTramadol

Unsafe

Avoid

There is considerable risk of physical harm when taking these combinations, they should be avoided where possible.

Caution

Use caution

These combinations are not usually physically harmful, but may produce undesirable effects, such as physical discomfort or overstimulation. Extreme use may cause physical health issues. Synergistic effects may be unpredictable. Care should be taken when choosing to use this combination.

DXMKetamineMXE
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Tolerance

Tolerance timelines are rules of thumb, not exact schedules, and vary widely between individuals and use patterns.

Cross Tolerance

Benzodiazepines, GABAergic depressants

Harm Potential

Addiction & Dependence

Psychological

Classified as habit-forming, indicating potential for psychological dependence.citation needed

History & Culture

Desmethylflunitrazepam was originally identified as an active metabolite of flunitrazepamcitation needed, the potent benzodiazepine marketed under trade names such as Rohypnol. The compound has since emerged on the grey market as a designer drug, sold online as a research chemical under names including fonazepam and the research designation Ro05-4435.

Legality

International

As of 23 August 2026, Desmethylflunitrazepam is not listed under the international drug-control conventions. INCB's current benzodiazepine identity annex identifies it exactly as CAS 2558-30-7, with alternative names Norflunitrazepam, Ro 5-4435, and Fonazepam, chemical name 5-(2-fluorophenyl)-7-nitro-1,3-dihydro-1,4-benzodiazepin-2-one, and InChIKey KNGIGRDYBQPXKQ-UHFFFAOYSA-N, but assigns no convention or schedule in the international-control column. Exact-name, synonym, CAS-number, chemical-name, and InChIKey searches found no corresponding entry in the complete current Yellow, Green, or Red Lists. The Green List separately places flunitrazepam in Schedule III under a chemical designation containing a 1-methyl group; that named substance is chemically distinct from desmethylflunitrazepam, and the Green List extends control to salts and qualifying stereoisomers, not to N-desmethyl analogues. The only March 2026 addition to the 1971 Convention is MDMB-FUBINACA, effective 25 November 2026, and it does not cover desmethylflunitrazepam.

By Country

Illegal11
Canada flagCanadaIllegal (analog/blanket ban)
Czech Republic flagCzech RepublicIllegal
France flagFranceIllegal
Germany flagGermanyIllegal (analog/blanket ban)
Ireland flagIrelandIllegal (analog/blanket ban)
Mexico flagMexicoIllegal (analog/blanket ban)
Poland flagPolandIllegal (analog/blanket ban)
South Africa flagSouth AfricaIllegal (analog/blanket ban)
Sweden flagSwedenIllegal
Turkey flagTurkeyIllegal
United Kingdom flagUnited KingdomIllegal
Controlled / restricted1
Russia flagRussiaRestricted
Prescription3
Austria flagAustriaPrescription only
New Zealand flagNew ZealandPrescription only
Singapore flagSingaporePrescription only
Legal / decriminalized2
Australia flagAustraliaLegal (regulated)
Italy flagItalyDecriminalized
Not scheduled1
United States flagUnited StatesNot scheduled

References

Source Pages

  1. PsychonautWiki: Benzodiazepines
  2. TripSit: Drug Combinations Chart
  3. TripSit: Wiki - Desmethylflunitrazepam entry
  4. Wikipedia

Citations

  1. Bjoern Moosmann, Philippe Bisel, Florian Franz, Laura M. Huppertz, & Volker Auwärter. (November 2016). Characterization and in vitro phase I microsomal metabolism of designer benzodiazepines - an update comprising adinazolam, cloniprazepam, fonazepam, 3-hydroxyphenazepam, metizolam and nitrazolam. Journal of Mass Spectrometry, 51(11), 1080–1089. https://doi.org/10.1002/jms.38401
  2. Maria Katselou, Ioannis Papoutsis, Panagiota Nikolaou, Chara Spiliopoulou, & Sotiris Athanaselis. (2016). Metabolites replace the parent drug in the drug arena. The cases of fonazepam and nifoxipam. Forensic Toxicology, 35(1), 1–10. https://doi.org/10.1007/s11419-016-0338-51
  3. Kilicarslan T, Haining RL, Rettie AE, Busto U, Tyndale RF, & Sellers EM. (April 2001). Flunitrazepam metabolism by cytochrome P450S 2C19 and 3A4. Drug Metabolism and Disposition, 29(4 Pt 1), 460–5. http://dmd.aspetjournals.org/content/29/4/460.long1
  4. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. legislation.gov.au (n.d.). https://www.legislation.gov.au/F2026L006331
  5. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. legislation.gov.au (n.d.). https://www.legislation.gov.au/F2026L00633/latest/versions1
  6. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. legislation.gov.au (n.d.). https://www.legislation.gov.au/F2026L00633/asmade/2026-05-28/text/original/epub/OEBPS/document_1/document_1.html1
  7. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. pubchem.ncbi.nlm.nih.gov (n.d.). https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/520217/synonyms/JSON1
  8. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. pubchem.ncbi.nlm.nih.gov (n.d.). https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/520217/property/IUPACName,MolecularFormula,CanonicalSMILES,IsomericSMILES/JSON1
  9. Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026, section 7(c) and Schedule 8 entry FLUNITRAZEPAM. pubchem.ncbi.nlm.nih.gov (n.d.). https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/3380/property/IUPACName,MolecularFormula,CanonicalSMILES,IsomericSMILES/JSON1
  10. Rezeptpflichtverordnung, Anlage 1. ris.bka.gv.at (n.d.). https://ris.bka.gv.at/eli/bgbl/1973/475/ANL1/NOR402731951

Further Reading

  1. EMCDDA Drug Profile: Desmethylflunitrazepam
  2. HØiseth et al., 2016. Detection times of flunitrazepam and norflunitrazepam in plasma and urine
  3. PubChem: Norflunitrazepam compound summary
  4. User experience reports compilation (Reddit, 2023)

Article Status

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    An autonomous workflow built by Josie Kins compiled this article's foundation from information published across the web.

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Recent changes8 human edits · latest

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19 August 2026

  1. Lyrea · Added a citation in PharmacologyPharmacokinetics

  2. Lyrea · Reworded 9 words in PharmacologyPharmacokinetics

  3. Lyrea · Updated the article

  4. Lyrea · Reworded 8 words in PharmacologyPharmacokinetics

24 January 2026

  1. Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more

  2. Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more

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