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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.
Phenazepam
7-Bromo-5-(2-chlorophenyl)-1,3-dihydro-1,4-benzodiazepine-2-one
Bonsai, Soviet Benzo, Fenaz, Panda, Bromdihydrochlorphenylbenzodiazepine
Phenazepam is a benzodiazepine first developed in the Soviet Union in 1975.citation needed It is prescribed in Russia and other countries for psychiatric conditions including anxiety and schizophrenia, as well as for epilepsy, alcohol withdrawal, and surgical premedication. Phenazepam is notable for its exceptionally long duration of action and high potency. The substance has gained notoriety for problematic recreational use, with numerous reports of compulsive redosing and reckless behavior due to its subtle onset and extended effects.
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
Threshold~0.5 mg
Light0.5-1 mg
Moderate1-2 mg
Strong2-3 mg
Heavy3+ mg
Bioavailability
80%1
Duration
Onset15-60 minutes
After Effects36 hours
Total18 hours
Subjective Effects
Legacy content. A statistically backed ontology from Mindstate Design Labs is coming soon.
The experience is dominated by heavy sedation, anxiolysis, and physical relaxation, with no reported alteration of sensory perception. Coordination becomes unreliable, and at higher doses recall of the period following ingestion can be substantially impaired.
Physical
Muscle relaxation, drowsiness, and hypnotic sedation are the primary physical effects, accompanied by dizziness and loss of coordination.
Cognitive
Anxiety is reduced and the mental state is markedly sedated, with anterograde amnesia becoming pronounced as dose increases.
Pharmacology
Pharmacodynamics
Phenazepam acts as a positive allosteric modulator at the benzodiazepine site of the GABA-A receptor.citation needed It is considerably more potent than diazepam, potentiating GABA responses with an EC50 of 6.1 nM in rat cerebellar slices versus 13.5 nM for diazepam. About 1 mg of phenazepam is reported to be equivalent to up to 10 mg of diazepam. The metabolite 3-hydroxyphenazepam is also pharmacologically active and potentiates GABA responses. The metabolites ABPH and QNZ exhibit biphasic activity at the GABA-A receptor, initially potentiating GABA at low concentrations and then inhibiting it at higher micromolar concentrations, so they are only likely to produce significant effects in overdose. ABPH is also thought to act at glycine and NMDA receptors at high micromolar concentrations.
Pharmacokinetics
Phenazepam is eliminated primarily by hepatic metabolism, with combined in silico and in vitro evidence identifying CYP3A4 as the most probable enzyme responsible and CYP3A5 as a possible contributor that could not be excluded.citation needed The main pathway is aromatic hydroxylation to 3-hydroxyphenazepam, alongside hydrolysis and glucuronide conjugation. After oral administration, phenazepam reaches a peak plasma concentration at about 4 hours and has an estimated bioavailability of roughly 80%. Its elimination half-life is reported between about 15 and 60 hours, spanning an oral estimate of roughly 60 hours and 14.9-15.6 hours following intramuscular or intravenous administration. The volume of distribution is 4.7-6.0 L and plasma clearance is 220.4-267.9 ml/h. In vitro, phenazepam also produced an observed but not statistically significant increase in CYP2B6 activity.
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.
Full Tolerance
Tolerance develops with regular use.citation needed Treatment courses are typically limited to two weeks due to the risk of dependence, suggesting clinically significant tolerance develops within this timeframe.
Cross Tolerance
Benzodiazepines2, GABAergic depressantscitation needed
Harm Potential
Addiction & Dependence
Psychological
HighHigh abuse potential with significant risk of psychological dependence.citation needed Anecdotal reports indicate a notable suggestibility for compulsive redosing and reckless usage patterns, particularly due to the drug's subtle onset and amnestic effects.
Physical
HighPhysical dependence develops with regular use, and treatment courses are typically limited to two weeks due to dependence risk.citation needed Abrupt discontinuation following prolonged use can cause severe withdrawal symptoms including restlessness, anxiety, insomnia, seizures, convulsions, and potentially death. Due to its intermediate half-life and active metabolites, withdrawal symptoms may take two or more days to manifest.
Seizure Risk
Seizures and convulsions are documented withdrawal symptoms following abrupt discontinuation of prolonged use.3 Gradual dose reduction is necessary to prevent withdrawal-induced seizures.citation needed
History & Culture
Phenazepam is a benzodiazepine that was first developed in the Soviet Union in 1975.4 The synthesis method was developed at the Physico-Chemical Institute of the Academy of Sciences of the Ukrainian SSR during the 1970s. The substance is now produced in Russia and several…
Legality
By Country
Illegal4
CanadaIllegal (analog/blanket ban)Phenazepam is covered by Schedule IV's category for benzodiazepines, their salts and derivatives. The Controlled Drugs and Substances Act prohibits unauthorized trafficking, importation, exportation, and production of Schedule IV substances. Schedule IV is not included in the Act's simple-possession prohibition, but obtaining a Schedule IV substance from a practitioner is regulated.
NetherlandsIllegalOpiumwet, lijst II19
Phenazepam is listed as ‘fenazepam’ in List II of the Opiumwet, with the chemical description 7-bromo-5-(2-chlorophenyl)-1,3-dihydro-2H-1,4-benzodiazepin-2-one. Article 3 prohibits import, export, preparation, sale, supply, transport, possession and manufacture of List II substances.
SwedenIllegalFörordning (1992:1554) om kontroll av narkotika, bilaga 121
Phenazepam is listed as “fenazepam” in Annex 1 under sleeping and sedative substances. Section 2 provides that substances in Annex 1 are deemed narcotics under the Narcotic Drugs Criminal Act.
United KingdomIllegalPhenazepam is controlled as a Class C drug under the Misuse of Drugs Act 1971 and in Schedule 3 to the Misuse of Drugs Regulations 2001. Its possession, supply, production, importation, and exportation are regulated under the United Kingdom's controlled-drugs legislation.
Controlled / restricted4
ColombiaRestrictedResolución 000116 de 20268
Colombia lists fenazepam as a substance of special control and subject to fiscalization in Resolution 000116 of 2026. The resolution places it in Lista Verde, Lista IV, the national implementation of the international psychotropic control listing.
DenmarkRestrictedBekendtgørelse om euforiserende stoffer (BEK nr. 405 af 26. marts 2026), Bilag 1, Liste E, nr. 339
Fenazepam is expressly listed in Liste E, nr. 33. Liste B, D og E omfatter stoffer, der kun må benyttes til medicinsk og videnskabelig brug. The regulation entered into force on 29 March 2026 and repealed BEK nr. 2446 of 12 December 2021.
LatviaRestrictedPhenazepam (Fenazepāms; CAS 51753-57-2) is named in Latvia's controlled-substances III List, for dangerous psychotropic substances liable to misuse. Latvia applies controls to listed substances and their derivatives, isomers, structural analogues, active metabolites, esters, ethers, salts, and medicines containing them; licensed pharmaceutical activity is required for dealings with III List substances and medicines.
UkraineRestrictedПро затвердження переліку наркотичних засобів, психотропних речовин і прекурсорів, постанова Кабінету Міністрів України від 06.05.2000 № 770 (чинна редакція від 07.06.2026)22
Phenazepam is subject to restricted circulation in Ukraine.
Prescription5
FrancePrescription onlyArrêté du 4 novembre 2016 modifiant l’arrêté du 22 février 1990 fixant la liste des substances psychotropes10
Le phénazépam figure sur la liste française des substances psychotropes. La liste consolidée de l’ANSM le rattache à l’arrêté du 4 novembre 2016 modifiant l’arrêté du 22 février 1990.
LithuaniaPrescription onlyLithuanian Minister of Health Order No. 5 of 6 January 2000, On Approval of the Lists of Narcotic and Psychotropic Substances, current consolidated edition effective 18 June 2025 (List III); Lithuanian Minister of Health Order No. V-700 of 29 July 2025 amending Order No. 112 on prescription writing and dispensing rules, effective 7 November 2025.161718
Lithuanian law establishes List III medical-use control and prescription handling for phenazepam. Phenazepam is a prescription-only controlled psychotropic material.
Legal / decriminalized1
BelarusLegal (regulated)Republican list of narcotic drugs, psychotropic substances and their precursors subject to state control in the Republic of Belarus (consolidated through Ministry of Health Resolution No. 18 of 10 March 2026)5
The current Belarus list subjects phenazepam to controlled circulation but does not specify indications for epilepsy or alcohol withdrawal.
References
Source Pages
Citations
- Peter D. Maskell, Giorgia De Paoli, L. Nitin Seetohul, & Derrick J. Pounder. (April 2012). Phenazepam: the drug that came in from the cold. Journal of Forensic and Legal Medicine, 19(3), 122–5. https://doi.org/10.1016/j.jflm.2011.12.0141
- Addiction: Part I. Benzodiazepines — Side Effects, Abuse Risk and Alternatives. American Family Physician, April 2000.. (n.d.). https://www.aafp.org/pubs/afp/issues/2000/0401/p2121.html1
- Phenazepam 1 mg Tablets — Arpimed Prescribing Information. (n.d.). https://arpimed.am/phenazepam-1-mg-tablets/1
- Phenazepam Pre-Review Report, Agenda Item 5.8 — WHO Expert Committee on Drug Dependence, 37th Meeting. (2015). https://ecddrepository.org/sites/default/files/2023-04/5.8_phenazepam_prerev.pdf1
- Republican list of narcotic drugs, psychotropic substances and their precursors subject to state control in the Republic of Belarus (consolidated through Ministry of Health Resolution No. 18 of 10 March 2026). eec.eaeunion.org (n.d.). https://eec.eaeunion.org/upload/medialibrary/8fe/aqdeegj1xqca147n47vc4it72nlo2pok/BY_2026.pdf1
- Controlled Drugs and Substances Act, Schedule IV. laws-lois.justice.gc.ca (n.d.). https://laws-lois.justice.gc.ca/eng/acts/C-38.8/section-sched95660.html1
- Controlled Drugs and Substances Act. laws-lois.justice.gc.ca (n.d.). https://laws-lois.justice.gc.ca/eng/acts/C-38.8/FullText.html1
- Resolución 000116 de 2026. minsalud.gov.co (n.d.). https://www.minsalud.gov.co/Normatividad_Nuevo/Resolucion%20No%20116%20de%202026.pdf1
- Bekendtgørelse om euforiserende stoffer (BEK nr. 405 af 26. marts 2026). retsinformation.dk (n.d.). https://www.retsinformation.dk/eli/lta/2026/405/pdf1
- Arrêté du 4 novembre 2016 modifiant l’arrêté du 22 février 1990 fixant la liste des substances psychotropes. ansm.sante.fr (n.d.). https://ansm.sante.fr/uploads/2026/07/03/20260703-psychotropes-liste-consolidee.pdf1
Further Reading
Article Status
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