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Clinical data
Other names4-Acetoxy-N,N-dimethyltryptamine, 3-(2'-dimethylaminoethyl)-4-acetoxy-indole[1]
Routes of
Oral, IV, intranasal, rectal
ATC code
  • none
Legal status
Legal status
  • AU: S9 (Prohibited substance)
  • BR: Class F2 (Prohibited psychotropics)
  • CA: Unscheduled
  • DE: NpSG (Industrial and scientific use only)
  • UK: Class A
  • US: Unscheduled
  • 3-[2-(Dimethylamino)ethyl]-1H-indol-4-yl acetate
CAS Number
PubChem CID
CompTox Dashboard (EPA)
Chemical and physical data
Molar mass246.310 g·mol−1
3D model (JSmol)
Melting point172 to 173 °C (342 to 343 °F)
  • CC(=O)Oc2cccc1[nH]cc(CCN(C)C)c12
  • InChI=1S/C14H18N2O2/c1-10(17)18-13-6-4-5-12-14(13)11(9-15-12)7-8-16(2)3/h4-6,9,15H,7-8H2,1-3H3 checkY

O-Acetylpsilocin (also known as psilacetin, 4-acetoxy-DMT, 4-AcO-DMT, or synthetic shrooms) is a semi-synthetic psychoactive drug that has been suggested by David Nichols to be a potentially useful alternative to psilocybin for pharmacological studies, as they are both believed to be prodrugs of psilocin.[2][3] However, some users report that O-acetylpsilocin's subjective effects differ from those of psilocybin and psilocin.[4][5] Additionally, some users prefer 4-AcO-DMT to natural psilocybin mushrooms due to feeling fewer adverse side effects such as nausea and heavy body load, which are more frequently reported in experiences involving natural mushrooms.[6] It is the acetylated form of the psilocybin mushroom alkaloid psilocin and is a lower homolog of 4-AcO-MET, 4-AcO-DET, 4-AcO-MiPT and 4-AcO-DiPT.


O-Acetylpsilocin (psilacetin) and several other esters of psilocin were patented on January 16, 1963, by Sandoz Ltd via Albert Hofmann & Franz Troxler.[1][7] Despite this, psilacetin remains a psychedelic compound with a limited history of use. It is theorized to be a prodrug of psilocin, as is psilocybin, which occurs naturally in many species of psychedelic mushrooms. This is because the aromatic acetyl moiety on the 4th position of the indole ring system is subject to deacetylation in acidic conditions such as those found in the stomach.[8] Psilacetin is O-acetylated psilocin, whereas psilocybin is O-phosphorylated.


O-Acetylpsilocin can be obtained by acetylation of psilocin under alkaline or strongly acidic conditions. It is, therefore, a synthetic compound. It is believed to be a prodrug of psilocin; however, speculation exists that psilacetin itself also may be psychoactive. O-Acetylpsilocin is more resistant than psilocin to oxidation under basic conditions due to its acetoxy group. While O-acetylpsilocin is not well researched (sometimes viewed negatively as a research chemical, as opposed to psilocin and psilocybin), it is not as difficult as psilocybin to synthesize. Due to their similar proposed mechanisms of action, this factor may provide further support for the proposition that O-acetylpsilocin might serve as an appropriate substitute for psilocybin in research of the application of psychedelic compounds in medicine.[2]

Given enough time in unfavorable conditions, O-acetylpsilocin can sometimes turn into a degraded form which is brown in color and can even progress into a brown/black tar-like substance. Researchers hypothesize this is a polymerization reaction and is said to have no effect on the potency of the substance. Preliminary GCMS analysis of the closely related homolog 4-acetoxy-DET suggests that this degraded form of O-acetylpsilocin consists mainly of the hydroxy form of the parent molecule.[9]


See psilocin for more details.

In the body, O-acetylpsilocin is deacetylated to psilocin by deacetylases/acetyltransferases during first pass metabolism[citation needed] and during subsequent passes through the liver (evident as psilacetin is also active via parenteral routes of ingestion).

Claims of subjective differences in effects between the acetylated and non-acetylated forms of psilocin vary:[4] some users report that O-acetylpsilocin lasts slightly longer, whilst others report that it lasts for a considerably shorter time. Many users report less body load and nausea compared with psilocin. Some users find that the visual effects produced by O-acetylpsilocin more closely resemble those produced by DMT than those produced by psilocin or psilocybin. These differences could be possible if psilacetin is psychoactive in itself and not merely as a prodrug. Despite this, there have been no controlled clinical studies to distinguish among the phenomenological effects of psilacetin, psilocin, and psilocybin.

4-AcO-DMT shown in powder form


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O-Acetylpsilocin can be considered an analog of psilocin making it a Schedule 9 prohibited substance in Australia under the Poisons Standard (October 2015).[10] A Schedule 9 substance is a substance which may be abused or misused, the manufacture, possession, sale or use of which should be prohibited by law except when required for medical or scientific research, or for analytical, teaching or training purposes with approval of Commonwealth and/or State or Territory Health Authorities.[10]

United States

O-Acetylpsilocin is ambiguously legal for use as a lab reagent or research chemical; however, it is an acetate ester of psilocin, meaning it would be considered akin to a Schedule I Controlled Substance under the Federal Analogue Act if sold for human consumption.

United Kingdom

O-Acetylpsilocin, being an ester of psilocin, is a Class A drug in the UK under the Misuse of Drugs Act 1971.[11]

Czech Republic

O-Acetylpsilocin is prohibited in Czech republic except strictly limited research and therapeutical purposes.[12]


O-Acetylpsilocin is illegal in Italy as it is an ester of a prohibited substance.


The Riksdag added 4-AcO-DMT to Narcotic Drugs Punishments Act under swedish schedule I ("substances, plant materials and fungi which normally do not have medical use" ) as of January 25, 2017, published by Medical Products Agency (MPA) in regulation HSLF-FS 2017:1 listed as 4-acetoxi-N,N-dimetyltryptamin.[13]


O-Acetylpsilocin is technically illegal in Israel as of being a derivative of DMT.

See also


  1. ^ a b US patent 3075992, Hofmann A, Troxler F, "Esters of indoles", assigned to Sandoz Ltd. 
  2. ^ a b Nichols D, Fescas S (1999). "Improvements to the Synthesis of Psilocybin and a Facile Method for Preparing the O-Acetyl Prodrug of Psilocin" (PDF). Synthesis. 1999 (6): 935–938. CiteSeerX doi:10.1055/s-1999-3490. S2CID 32044725. Archived (PDF) from the original on 17 February 2012. Retrieved 17 January 2012.
  3. ^ Bauer BE (2019-09-18). "The State of the Art of Psilacetin (4-AcO-DMT)". Psychedelic Science Review. Retrieved 2021-02-13.
  4. ^ a b "4-AcO-DMT (also 4-acetoxy-N,N-dimethyltryptamine) : Erowid Exp: Main Index". Archived from the original on 2010-07-28.
  5. ^ Janikian M (2020-05-26). "The Complete Guide: 4-AcO-DMT a.k.a. Synthetic Shrooms". DoubleBlind Mag.
  6. ^ Palamar JJ, Acosta P (January 2020). "A qualitative descriptive analysis of effects of psychedelic phenethylamines and tryptamines". Human Psychopharmacology. 35 (1): e2719. doi:10.1002/hup.2719. PMC 6995261. PMID 31909513.
  7. ^ US 3075992 
  8. ^ Staněk J, Černá MJ (January 1963). "Acidic deacetylation of sugar acetates". Tetrahedron Letters. 4 (1): 35–7. doi:10.1016/S0040-4039(01)90572-6.
  9. ^ "Erowid 4-Acetoxy-DET Vaults : 4-Acetoxy-DET / Ethacetin Degradation". Retrieved 10 September 2023.
  10. ^ a b "Poisons Standard October 2015". Federal Register of Legislation. Australian Government. 30 September 2015. Archived from the original on 2016-01-19. Retrieved 2016-01-06.
  11. ^ Misuse of Drugs Act 1971 (Schedule 2 Part I). 1971.
  12. ^ "Government regulation of the list of the addictive substances". Federal Register of Legislation. Czech Government.
  13. ^ "Föreskrifter om ändring i Läkemedelsverkets föreskrifter (LVFS 2011:10) om förteckningar över narkotika" [Regulations on changes in the Swedish Medicines Agency's regulations (LVFS 2011:10) on lists of narcotics] (PDF) (in Swedish). Archived (PDF) from the original on 2017-10-31. Retrieved 2017-04-21.