Acetylfentanyl
Acetylfentanyl is a synthetic opioid of the anilidopiperidine class and a structural analog of fentanyl.1 Originally described in the 1960s alongside fentanyl itself, it has never been approved for medical use and has only appeared on the illicit market as a designer drug.1 It is estimated to be several times more potent than heroin12 yet roughly fifteen times less potent than fentanyl, still presenting significant overdose risk.1
Contents
Dosage & Duration
Dosage
Duration
Subjective Effects
The experience is that of a potent, short-acting opioid, dominated by sedation, pain relief, and a relaxed, mood-lifted state. Notably, many users find its euphoria muted relative to typical recreational opioids, a quality it shares with fentanyl. The margin between an active dose and dangerous respiratory depression is narrow, and heavy doses readily progress into somnolence and unconsciousness.
Physical
A heavy, relaxed body state with pronounced pain relief is central to the experience. This is accompanied by the standard opioid side-effect profile of itchiness, nausea, constipation, dry mouth, and constricted pupils, with dose-dependent respiratory depression as the principal danger.
Sedation
Sedation is a core component, scaling from drowsiness and somnolence through fatigue and weakness into unconsciousness at heavy doses.
Cognitive
The headspace is relaxed, dulled, and content, with slowed attention and reduced mental clarity. Confusion, changes in focus, and occasional nervousness or anxiety are reported alongside the mood lift.
Emotional
Mood lift and relaxation are typical, though the euphoric component is often described as underwhelming.
Suppressions
Reagent Testing
Loading reagent data
Pharmacology
Pharmacodynamics
Acetylfentanyl acts as a μ-opioid receptor agonist3, producing its effects through binding at the same receptor sites engaged by endogenous endorphins. Its high lipophilicity allows it to penetrate the central nervous system more readily than many other opioids, contributing to its potency.3 In animal studies using selective antagonists, its activity was confirmed to be mediated primarily through the μ-opioid receptor; a δ-opioid antagonist did not alter its effects, while a μ-opioid antagonist reduced them and naltrexone fully reversed them.3 Acetylfentanyl has been estimated to be approximately 15 times more potent than morphine as an analgesic (with an ED50 of 0.021 mg/kg in the mouse acetic acid writhing test) and roughly 15 times less potent than fentanyl.31
Pharmacokinetics
Acetylfentanyl's high lipophilicity, its ability to dissolve in fats and lipids, allows it to penetrate the central nervous system more readily than many other opioids, contributing to its potency relative to morphine.
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
Opioids (all classes)
Harm Potential
Addiction & Dependence
Psychological
HighAcetylfentanyl presents an extremely high risk of addiction and abuse, and its use can lead to psychological dependence.4 Compulsive redosing is commonly reported, especially because its effects are short-lived.
Physical
Extremely HighChronic use leads to extreme physical dependence. Cravings and withdrawal symptoms occur upon sudden cessation. Animal studies have demonstrated that acetylfentanyl can completely suppress morphine withdrawal symptoms, confirming significant cross-dependence liability with other opioids.
Toxicity
Animal toxicity studies observed significant bleeding in the small intestines of mice administered acetylfentanyl; the relevance of this finding to human use at typical doses remains unclear.
Respiratory depression occurs at doses proportionally closer to the psychoactive range than with many other opioids; this effect can rapidly progress to fatal anoxia, with pulmonary edema documented in overdose fatalities.6
History & Culture
Discovery and Early History
Acetylfentanyl was first described in patents from Research Laboratorium Dr. C. Janssen (Janssen Pharmaceutica), a Belgian pharmaceutical company. Its analgesic activity was characterized in a 1968 patent by Paul Janssen, the company's founder. The compound was discovered contemporaneously with…
Legality
International
1961 Single Convention: acetylfentanyl is controlled in Schedules I and IV.
1971 Convention on Psychotropic Substances: acetylfentanyl is not scheduled.
1988 Convention: acetylfentanyl is not listed in precursor Tables I or II.
By Country
References
Source Pages
Citations
- Mohr ALA, Friscia M, Papsun D, Kacinko SL, Buzby D, & Logan BK. (2016). Acetyl Fentanyl, a Novel Fentanyl Analog, Causes 14 Overdose Deaths in Rhode Island, March–May 2013. Journal of Analytical Toxicology. https://pmc.ncbi.nlm.nih.gov/articles/PMC4469714/123456
- (n.d.). Acetyl Fentanyl Overdose Fatalities — Rhode Island, March–May 2013 (MMWR). https://pmc.ncbi.nlm.nih.gov/articles/PMC4604997/1
- European Monitoring Centre for Drugs Drug Addiction, & European Police Office. (June 2016). EMCDDA–Europol Joint Report on acetylfentanyl. European Monitoring Centre for Drugs and Drug Addiction (EMCDDA). https://doi.org/10.2810/8906941234567891011121314
- Drug Enforcement Administration. (July 2015). Acetyl fentanyl. Drug Enforcement Administration Office of Diversion Control. http://www.deadiversion.usdoj.gov/drug_chem_info/acetylfentanyl.pdf1
- (June 2008). Studies on 1-(2-phenethyl)-4-(''N''-propionylanilino)piperidine (fentanyl) and its related compounds. VI. Structure-analgesic activity relationship for fentanyl, methyl-substituted fentanyls and other analogues. Forensic Toxicology, 26(1), 1–5. https://doi.org/10.1007/s11419-007-0039-112
- (October 2016). A fatal poisoning case by intravenous injection of "bath salts" containing acetyl fentanyl and 4-methoxy PV8. Forensic Science International, 267, e6–e9. https://doi.org/10.1016/j.forsciint.2016.08.02512
- (2015). Schedules of Controlled Substances: Temporary Placement of Acetyl Fentanyl Into Schedule I. Drug Enforcement Administration / Federal Register. https://www.govinfo.gov/content/pkg/FR-2015-07-17/html/2015-17563.htm12
- Centers for Disease Control Prevention (CDC). (August 2013). Acetyl fentanyl overdose fatalities--Rhode Island, March-May 2013. MMWR. Morbidity and Mortality Weekly Report, 62(34), 703–4. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6234a5.htm1
- (June 2015). Acetyl Fentanyl, a Novel Fentanyl Analog, Causes 14 Overdose Deaths in Rhode Island, March-May 2013. Journal of Medical Toxicology, 11(2), 208–17. https://doi.org/10.1007/s13181-015-0477-91
- (July 2015). Fentanyls: Are we missing the signs? Highly potent and on the rise in Europe. The International Journal on Drug Policy, 26(7), 626–31. https://doi.org/10.1016/j.drugpo.2015.04.0031
- (n.d.). Controlled Drugs and Substances Act, Schedule I. laws-lois.justice.gc.ca. https://laws-lois.justice.gc.ca/eng/acts/C-38.8/page-17.html1
- (2025). Controlling Fentanyl-Related Substances – China's Contribution (White Paper). People's Republic of China / Consulate General. https://erbil.china-consulate.gov.cn/eng/zgxw/202503/t20250305_11568662.htm1
- (n.d.). Betäubungsmittelgesetz, Anlage I. gesetze-im-internet.de. https://www.gesetze-im-internet.de/btmg_1981/anlage_i.html1
- (n.d.). Misuse of Drugs Act 1971; Misuse of Drugs Regulations 2001. gov.uk. https://www.gov.uk/government/publications/controlled-drugs-list--2/list-of-most-commonly-encountered-drugs-currently-controlled-under-the-misuse-of-drugs-legislation1
- (n.d.). 21 CFR § 1308.11(d). ecfr.gov. https://www.ecfr.gov/current/title-21/chapter-II/part-1308/section-1308.111
Further Reading
Automated synthesisInformation aggregated and synthesized using an autonomous workflow built by Josie Kins.
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