Fentanyl

N-(1-Phenethylpiperidin-4-yl)-N-phenylpropanamide

Fent, Fenty, Fetty, Apache, China Girl

Psychoactive Class

Chemical Class

Fentanyl is a synthetic opioid¹ of the anilidopiperidine class first synthesized by Paul Janssen in 1960² and approved for medical use in the United States in 1968². It is approximately 80 to 100 times more potent than morphine¹ and is used clinically for anesthesia² and breakthrough cancer pain². Fentanyl is widely encountered as an adulterant in illicit drug supplies, particularly heroin¹, where its extreme potency has contributed to numerous accidental overdoses and fatalities¹.

Dosage & Duration

Dosage

Threshold~5 ug

Light5-25 ug

Moderate25-50 ug

Strong50-75 ug

Heavy75+ ug

Bioavailability

~64%

Due to the compound's extreme potency, accurate measurement is critical and the margin for error is very narrow. The risk of fatal overdose is high, particularly from respiratory depression. Individuals without opioid tolerance should use substantially lower starting amounts.

Duration

Onset5-15 minutes

Total1-4 hours

Subjective Effects

Effects vary widely by individual, dose, and context.

Physical

Constipation Cough suppression Difficulty urinating Pupil constriction Decreased libido

Cognitive

Anxiety suppression Compulsive redosing

Forked from Subjective Effect Documentation work

by Josie KinsAugust 2016.

Reagent Testing

Loading reagent data

Expected colorimetric results are being prepared.

Pharmacology

Pharmacodynamics

Fentanyl is a potent μ-opioid receptor agonist, binding this target with 50 to 100 times greater potency than morphine.³ It also activates δ-opioid and κ-opioid receptors, though with considerably lower affinity and relatively modest functional contribution at these sites.³ Receptor activation triggers G-protein-coupled signaling that inhibits neuronal activity through decreased cAMP production and altered ion conductance. Its exceptionally high lipid solubility enables rapid penetration of the central nervous system, a principal factor underlying its potency relative to other opioids.⁴

Pharmacokinetics

Fentanyl undergoes extensive first-pass metabolism when taken orally, predominantly via CYP3A4-catalyzed N-dealkylation to norfentanyl, which accounts for approximately 99% of its biotransformation.⁵⁶ Minor pathways include amide hydrolysis and alkyl hydroxylation.⁶ All known metabolites are pharmacologically inactive.⁵ Fentanyl is 80 to 85% bound to plasma proteins, with a terminal half-life of approximately 7 hours.⁵³ Within 72 hours, roughly 75% of a dose is excreted in urine (less than 7% unchanged) and 9% in feces.³

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.

AlcoholBenzodiazepinesCocaineDXMGHB/GBLKetamineMXEPregabalinTramadol

Unsafe

Avoid

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

Diphenhydramine

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.

AmphetaminesMAOIsMephedroneNitrous oxidePCP

TripSit

Tolerance

Full Tolerance

Ongoing repeated fentanyl exposure can reduce responsiveness to many of its effects. This does not occur at the same speed for every effect; constipation-related tolerance tends to build particularly slowly compared with opioid effects such as euphoria and analgesia.

Baseline Reset

1-2 weeks

Half Tolerance

3-7 days

Cross Tolerance

All other opioids

Harm Potential

Addiction & Dependence

Psychological

Extremely High

Fentanyl is considered extremely addictive with a high potential for abuse.⁷ Its rapid onset and short duration of action lead to compulsive redosing, contributing to strong psychological dependence. The intense but brief euphoria creates powerful reinforcing patterns that drive continued use.⁷

Physical

Extremely High

Physical dependence develops rapidly with regular use.⁷ Withdrawal symptoms are severe and include seizures, sleep disorders, depression, anxiety, and intense cravings.⁸ Withdrawal should not be abrupt and requires medical supervision due to severity.⁷

Toxicity

Respiratory System

The primary acute danger is respiratory depression, which at overdose levels can cause anoxia, respiratory arrest, and death; this risk is substantially heightened in opioid-naive individuals and when combined with other CNS depressants.⁹ Wooden chest syndrome, a sudden rigidity of abdominal muscles and diaphragm causing complete respiratory failure, can occur with high doses and is believed to be the main cause of death in fentanyl overdoses.¹⁰

Cardiovascular

Acute cardiovascular effects including bradycardia and vasodilation occur during intoxication; these are generally not associated with long-term cardiac damage at appropriate doses and do not significantly affect cardiac contractility at regular doses.

Gastrointestinal

Constipation is one of the few long-term complications associated with appropriate fentanyl use; tolerance to this effect develops particularly slowly compared to other opioid effects.¹¹

Psychosis Risk

Hallucinations, delirium (including narcotic delirium), and confusion have been reported as adverse effects.³⁸ Post-acute withdrawal may include psychosis in extreme cases. These effects are relatively uncommon during typical use and are more associated with high doses, overdose, or withdrawal states.

Seizure Risk

Seizures are documented as a severe withdrawal symptom following chronic use and abrupt discontinuation, rather than as a direct effect of fentanyl intoxication.⁸ Withdrawal should be conducted gradually under medical supervision to minimize seizure risk.

History & Culture

Discovery and Synthesis

Fentanyl was first synthesized in 1959 by Belgian scientist Paul Janssen at Janssen Pharmaceutica, his relatively newly established pharmaceutical company.¹² The compound was developed through systematic screening of chemical analogues of pethidine (marketed as…

Legality

International

Fentanyl is a narcotic drug in Schedule I of the 1961 Single Convention as amended. It is not listed as a psychotropic substance in the 1971 Convention schedules and is not a listed precursor chemical in the 1988 Convention Tables I or II.

By Country

United StatesPrescription onlySchedule II

21 CFR 1308.12(c), Schedule II⁵⁸

Controlled under the Controlled Substances Act as a Schedule II opiate.⁵⁹⁶⁰ FDA approved for medical use since 1968. Illegal to sell without a DEA license and illegal to possess without a valid prescription. Certain formulations such as Abstral require distributors to implement FDA-approved risk evaluation and mitigation strategy (REMS) programs.

AustraliaPrescription onlySchedule 8 controlled drug

Therapeutic Goods (Poisons Standard—October 2025) Instrument 2025, Schedule 8²¹

Classified as a Schedule 8 controlled drug, meaning it is available for legitimate medical use under strict prescription controls.²² Additionally designated as a border controlled substance under Criminal Code Act 9.1.314, with further restrictions imposed by individual states and territories. Unauthorized possession, production, or supply is prohibited.

BelgiumPrescription onlyAnnex I

Royal Decree of 6 September 2017 regulating narcotic and psychotropic substances (consolidated Justel text)²⁵²⁶

Fentanyl is controlled in Annex I of Belgium’s Royal Decree of 6 September 2017, which incorporates the 1961 Convention Yellow List. The decree requires prior authorization for dealing in listed products and limits that authorization to medical or scientific purposes. A pharmacist may dispense an Annex I medicine to the public only on a lawfully obtained, signed, and dated medical prescription; that prescription must state the prescriber’s address, dose, number of units, dosage, and, where applicable, treatment duration.

CanadaPrescription onlySchedule I fentanyl

Controlled Drugs and Substances Act, Schedule I, item 16²⁹

Controlled under Schedule I of the Controlled Drugs and Substances Act.³⁰ Medical use requires prescription. In some jurisdictions such as Ontario, patients prescribed fentanyl patches must return used patches to pharmacies before receiving prescription refills as a diversion prevention measure.

FinlandIllegalLiite I

Valtioneuvoston asetus huumausaineina pidettävistä aineista, valmisteista ja kasveista 543/2008³³³⁴

Fentanyl is listed in Annex I to Government Decree 543/2008 on substances, preparations and plants regarded as narcotics. Under Finland's Narcotics Act, narcotics may not be produced, imported, exported, transported, transited, distributed, traded, possessed, or used except as permitted for medical, scientific, or other statutory purposes.

IrelandPrescription onlySchedule 2

Misuse of Drugs Regulations 2017 (S.I. No. 173/2017)³⁶³⁷

Fentanyl is listed in Schedule 2 of the Misuse of Drugs Regulations 2017, which have applied since 4 May 2017. Unauthorised production, supply, importation and exportation of a controlled drug are prohibited, and unauthorised possession is an offence. Schedule 2 fentanyl may be possessed for medical, dental or veterinary administration under a practitioner's directions and supplied by authorised practitioners and pharmacists.

MexicoPrescription onlyEstupefaciente

Ley General de Salud⁴⁰

Fentanyl is classified as an estupefaciente in Article 234 of Mexico's Ley General de Salud. Acts involving estupefacientes are subject to the law's health-control regime, and medical prescriptions for them must use special prescription forms issued to authorized professionals.

New ZealandIllegalClass A

Misuse of Drugs Act 1975⁴³

Fentanyl is listed as a Class A controlled drug in Schedule 1 of the Misuse of Drugs Act 1975. The Act makes the unauthorised import, export, production, manufacture, supply, administration, sale, and possession of a Class A controlled drug an offence.

PolandPrescription onlyI-N

Rozporządzenie Ministra Zdrowia z dnia 17 sierpnia 2018 r. w sprawie wykazu substancji psychotropowych, środków odurzających oraz nowych substancji psychoaktywnych (Dz.U. 2018 poz. 1591), załącznik nr 2⁴⁶⁴⁷

Fentanyl is listed in Group I-N of the Polish Minister of Health's controlled-narcotics schedule, which entered into force on 21 August 2018. Group I-N narcotics may be used only for medical, industrial, or research purposes. Medicinal preparations containing narcotics are dispensed by pharmacies only on a specially marked prescription or requisition, and unauthorized possession is punishable by imprisonment of up to three years.

SingaporeIllegalClass A

Misuse of Drugs Act 1973⁴⁸

Fentanyl is listed as a Class A controlled drug in the First Schedule to Singapore's Misuse of Drugs Act 1973. The Act treats unauthorised possession, trafficking, manufacture, and import or export of controlled drugs as offences, subject to its statutory authorisations. The Class A entry also covers fentanyl compounds structurally derived from N-(1-Methyl-4-piperidyl)-N-phenyl formamide and salts of substances within that entry.

SwitzerlandPrescription onlyVerzeichnis a

Betäubungsmittelverzeichnisverordnung des EDI (BetmVV-EDI), Verzeichnis a⁵²

Specifically named in Verzeichnis A (List A) of controlled substances. Medicinal use is permitted with appropriate authorization, but non-medical possession and supply are prohibited.

UkrainePrescription onlyTable II List 1

Cabinet of Ministers of Ukraine Resolution No. 770 of 6 May 2000, On Approval of the List of Narcotic Drugs, Psychotropic Substances and Precursors⁵⁴⁵⁵

Fentanyl is listed in Table II, List No. 1 of Ukraine's List of Narcotic Drugs, Psychotropic Substances and Precursors, whose circulation is restricted. Narcotic medicines are dispensed through licensed pharmacies on a prescription issued by a treating physician.

ArgentinaPrescription onlyLista I

Resolución 2622/88 del Ministerio de Salud y Acción Social¹⁹²⁰

Fentanilo is listed in Lista I of Resolución 2622/88, which updates the controlled-narcotic lists under Ley 17.818. It is a medicinal substance used in human medicine and is prescribed for severe acute or chronic pain; non-medical use is illegal. The list also controls the substance's possible isomers, esters, ethers, and salts under the terms stated in the annex.

AustriaPrescription onlySuchtgift

Suchtgiftverordnung, Anhang I, I.1.b²³

Legal for medical use under the Arzneimittelgesetz (AMG). Unauthorized sale or possession without a prescription is illegal under the Suchtmittelgesetz (SMG, Narcotic Substances Act).²⁴

BrazilPrescription onlyLista A1

Portaria SVS/MS nº 344, de 12 de maio de 1998 (Anexo I, Atualização nº 101)²⁷²⁸

Fentanyl (fentanila) is listed in Lista A1 of Portaria SVS/MS nº 344/1998 as a narcotic subject to Notificação de Receita A. Dispensing a medicine containing a Lista A1 substance requires that prescription notification, and the pharmacy or drugstore may dispense it only when the notification and prescription are properly completed. Activities involving the controlled substance or medicines containing it require special authorization under the regulation.

Czech RepublicPrescription onlyFentanyl

Act No. 167/1998; Government Regulation No. 463/2013³¹³²

Fentanyl is listed in Annex 1 of the Government Regulation’s controlled-substances schedules. The Act classifies substances in Annexes 1–7 as controlled narcotic or psychotropic substances. A person acquires a controlled medicinal preparation for personal use only on a prescription or through a health-care provider. Annex 1 medicinal products are prescribed and dispensed only on an e-prescription marked ‘vysoce návyková látka’ or, exceptionally, a blue-stripe paper prescription.

GermanyPrescription onlyAnlage III

Betäubungsmittelgesetz, Anlage III³⁵

Listed in Anlage III of the Betäubungsmittelgesetz (Narcotics Act), indicating it is a marketable and prescription-capable narcotic.³⁵ Can only be prescribed using a special narcotic prescription form (Betäubungsmittelrezept).

ItalyPrescription onlyTabella I

DPR 309/1990, Tabella I³⁸

Listed in Tabella I of the official tables of narcotic and psychotropic substances maintained by the Ministry of Health.³⁹ Possession, purchase, and sale without authorization are illegal.

NetherlandsPrescription onlyLijst I

Opiumwet, lijst I⁴¹

Classified as a List I substance under the Opium Act.⁴² Medical use permitted with prescription, but unauthorized possession, production, and distribution are criminal offenses.

PhilippinesIllegalSchedule I

Republic Act No. 9165 (Comprehensive Dangerous Drugs Act of 2002)⁴⁴⁴⁵

Fentanyl is a dangerous drug under the Comprehensive Dangerous Drugs Act of 2002 because the Act incorporates the schedules annexed to the 1961 Single Convention on Narcotic Drugs, whose Schedule I lists fentanyl. Unauthorized importation, sale, delivery, manufacture, possession, and use of dangerous drugs are criminal offences; the Act preserves authorized medical use by licensed practitioners.

RussiaSchedule IICitation needed

Controlled as a Schedule II substance under Russian drug control legislation. Medical use permitted under strict controls; unauthorized possession and distribution are prohibited.

SpainRestrictedLista I estupefaciente

Ley 17/1967, de 8 de abril, art. 2; Convención Única de 1961, Lista I⁴⁹⁵⁰⁵¹

Fentanilo is a Lista I narcotic drug under the Single Convention framework applied in Spain by Ley 17/1967. Article 2(1) of that law treats substances in Convention Lists I and II as estupefacientes, while the AEMPS states that Lista I substances are subject to rigorous control and require an official narcotics prescription for dispensing. Authorised industrial, therapeutic, scientific and teaching uses remain permitted; this is not a blanket prohibition.

TurkeyRed prescription only

Designated as a 'red prescription' substance, the most restricted prescription category in Turkey.⁵³ Illegal to sell or possess without a valid prescription from an authorized physician.

United KingdomPrescription onlyClass A drug

Misuse of Drugs Act 1971, Schedule 2, Part I⁵⁶

Controlled under the Misuse of Drugs Act 1971.⁵⁷ Medical use permitted with appropriate prescription, but unauthorized possession, production, or supply carries severe criminal penalties.

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Fentanyl

N-(1-Phenethylpiperidin-4-yl)-N-phenylpropanamide

Fent, Fenty, Fetty, Apache, China Girl

Psychoactive Class

Opioid Sedative Depressant

Chemical Class

Anilidopiperidine (opioid)