WARNINGMIXING OR WITHDRAWAL CAN BE DANGEROUS
Ordinary doses in combination with other depressants can fatally stop breathing. After prolonged dependency, stopping suddenly can also cause seizures or delirium; seek medical help.
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.
Duration
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.
Suppressions
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
Dangerous
Highest riskThese 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.
Unsafe
AvoidThere is considerable risk of physical harm when taking these combinations, they should be avoided where possible.
Caution
Use cautionThese 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.
Tolerance
Tolerance timelines are rules of thumb, not exact schedules, and vary widely between individuals and use patterns.
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
References
Source Pages
Citations
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- Rezeptpflichtverordnung, Anlage 1. ris.bka.gv.at (n.d.). https://ris.bka.gv.at/eli/bgbl/1973/475/ANL1/NOR402731951
Further Reading
Article Status
Step 1 · Automated synthesisAn autonomous workflow built by Josie Kins compiled this article's foundation from information published across the web.
- Step 2 · First-pass review
A first pass manual review and edit of article prose and copy has been performed by subject-matter expert Lyrea. This does not guarantee factual accuracy. An additional human review for each of this article's citations is yet to be performed.
- Step 3 · Citation reviewPending
No one has reviewed this article's citations yet. That second pass checks each claim against the source it cites.
Recent changes8 human edits · latest
Times are UTCNewest first
19 August 2026
Lyrea · Added a citation in Pharmacology › Pharmacokinetics
Lyrea · Reworded 9 words in Pharmacology › Pharmacokinetics
Lyrea · Updated the article
Lyrea · Reworded 8 words in Pharmacology › Pharmacokinetics
24 January 2026
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
Josie Kins · Updated the article · also 1,4-Butanediol, 1B-LSD, 1cP-AL-LAD and 573 more
Suggest an edit
Spotted a mistake, an outdated claim, or something missing from the Desmethylflunitrazepam article? Send the editors a private note. Feedback lands in a moderation queue and is never shown on the site.
Wish to give generalised feedback? You can do so here.