white → orange2
Not yet reviewed — this article is pending editorial review by Lyrea.
WARNINGDANGER OF DEATH
High doses alone or ordinary doses in combination with other depressants can fatally stop breathing.
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4-Fluorobutyrfentanyl
4-Fluorobutyrfentanyl is a potent synthetic opioid and analog of butyrfentanyl that has been sold online as a designer drug. It is closely related to 4-fluorofentanyl. The substance is reportedly rare, and very little is known about its pharmacological profile or safety margins. It is generally administered as a nasal spray. Due to its extreme potency, it should be handled with great caution and never combined with other depressants.
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
Threshold~300 µg
Light300-600 µg
Moderate600-900 µg
Strong900-1200 µg
Heavy1200+ µg
Duration
Total30-60 minutes
Subjective Effects
Legacy content. A statistically backed ontology from Mindstate Design Labs is coming soon.
The experience is that of a classic opioid: a warm, euphoric mood lift paired with pain relief and pronounced physical relaxation, with little to no sensory alteration. As a fentanyl analog, its effect profile closely mirrors that of fentanyl itself, including the potential for serious, life-threatening respiratory depression.
Physical
The body feels relaxed and pain-free, accompanied by typical opioid side effects such as itchiness, dry mouth, constipation, and constricted pupils. Nausea can occur, and respiratory depression becomes a serious danger at higher doses.
Cognitive
The headspace is dominated by euphoria and an elevated, contented mood rather than any notable alteration of thought or perception.
Emotional
Pharmacology
Pharmacodynamics
4-Fluorobutyrfentanyl is an opioid analgesic and a structural analog of butyrfentanyl. It is described as an extremely potent fentanyl analog, though detailed pharmacological characterization of this specific compound remains limited. As an opioid analgesic, it is understood to act at μ-opioid receptors, though specific binding or functional data for 4-fluorobutyrfentanyl itself have not been published in the available literature.
Pharmacokinetics
Absorption & half-lifenot documented yetMetabolitesnone documented yet
Interactions
Interactions not written up yet
An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.
Tolerance
Tolerance timelines are rules of thumb, not exact schedules, and vary widely between individuals and use patterns.
Cross Tolerance
Opioids
Harm Potential
Addiction & Dependence
Psychological
HighClassified as habit-forming. As an extremely potent opioid and fentanyl analog, it carries significant potential for psychological addiction.
Physical
HighAs an opioid classified as habit-forming, physical dependence is expected with regular use.
Toxicity
Respiratory System
Potentially serious respiratory depression can occur during use and may be life-threatening, particularly given the extreme potency of this fentanyl analog.
History & Culture
4-Fluorobutyrfentanyl emerged as a designer drug sold online as part of the broader wave of synthetic opioid analogs appearing in illicit markets. Structurally, it is an analog of butyrfentanyl and is closely related to 4-fluorofentanyl, representing one of numerous modifications to the fentanyl…
Legality
By Country
Illegal3
United StatesIllegal21 C.F.R. § 1308.11(b)(93), Schedule I; 83 Fed. Reg. 4580 (Feb. 1, 2018); 84 Fed. Reg. 57323 (Oct. 25, 2019)91011
Under federal law, 4-fluorobutyrfentanyl, which the DEA lists as para-fluorobutyryl fentanyl under controlled-substance code 9823, is a Schedule I controlled substance. Its possession, manufacture, distribution, import, export, research, instructional use, and chemical analysis are federally controlled. The designation has applied since February 1, 2018, and has been permanent since October 25, 2019. State, territorial, tribal, and local controls may differ or add restrictions.
ChinaIllegal4-Fluorobutyrfentanyl has been controlled in China since 1 October 2015 and is expressly listed by name as item 114 of the current 2025 Catalogue of Non-Medicinal Narcotic Drugs and Psychotropic Substances. Its production, purchase, sale, transport, use, storage, import and export are prohibited. Experimental research may be conducted under the Regulations governing non-medicinal controlled substances.
SwedenIllegalSweden classifies 4-fluorobutyrfentanyl (4F-BF) as a narcotic in List I, which covers substances that normally have no medical use. The exact substance was added to Annex 1 by SFS 2019:24 with effect from 22 March 2019 and remains listed in the Medical Products Agency's consolidation through HSLF-FS 2026:26. Unauthorized possession, use, transfer, manufacture and other handling are criminal offences; penalties range from a fine or up to six months' imprisonment for a minor offence to six to ten years for an exceptionally serious offence.
References
Citations
- 我国管制毒品目录（2026年7月更新，540种+三大类）. ga.sz.gov.cn (n.d.). https://ga.sz.gov.cn/SZJDZX/SZBMFW/content/post_12898420.html1
- 非药用类麻醉药品和精神药品列管办法. gaj.panjin.gov.cn (n.d.). https://gaj.panjin.gov.cn/2015_10/08_00/content-235605.html1
- 麻醉药品和精神药品管理条例 (Regulations on the Administration of Narcotic Drugs and Psychotropic Substances), third revision. xzfg.moj.gov.cn (n.d.). https://xzfg.moj.gov.cn/front/law/detail?LawID=17441
- 三部门联合发布最新版《非药用类麻醉药品和精神药品目录》. btgaj.xjbt.gov.cn (n.d.). https://btgaj.xjbt.gov.cn/c/2025-07-28/8428464.shtml1
- SFS 2019:24, Förordning om ändring i förordningen (1992:1554) om kontroll av narkotika. svenskforfattningssamling.se (n.d.). https://svenskforfattningssamling.se/sites/default/files/sfs/2019-02/SFS2019-24.pdf1
- Läkemedelsverkets föreskrifter (LVFS 2011:10) om förteckningar över narkotika, consolidated through HSLF-FS 2026:26. lakemedelsverket.se (n.d.). https://www.lakemedelsverket.se/globalassets/dokument/lagar-och-regler/lvfs/lvfs-2011-10-konsoliderad.pdf1
- Förordning (1992:1554) om kontroll av narkotika. riksdagen.se (n.d.). https://www.riksdagen.se/sv/dokument-och-lagar/dokument/svensk-forfattningssamling/forordning-19921554-om-kontroll-av-narkotika_sfs-1992-1554/1
- Narkotikastrafflag (1968:64). riksdagen.se (n.d.). https://www.riksdagen.se/sv/dokument-och-lagar/dokument/svensk-forfattningssamling/narkotikastrafflag-196864_sfs-1968-64/1
- Electronic Code of Federal Regulations, Title 21, § 1308.11 — Schedule I (September 1, 2026 text). ecfr.gov (n.d.). https://www.ecfr.gov/api/renderer/v1/content/enhanced/2026-09-01/title-21?part=1308§ion=1308.111
- Schedules of Controlled Substances: Temporary Placement of Seven Fentanyl-Related Substances in Schedule I, 83 FR 4580. govinfo.gov (n.d.). https://www.govinfo.gov/content/pkg/FR-2018-02-01/html/2018-02008.htm1
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 reviewPending
Not yet reviewed — this article is pending editorial review by Lyrea.
- 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 changes7 human edits · latest
Times are UTCNewest first
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
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
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