4-Acetoxy-N,N-dimethyltryptamine (4-AcO-DMT or 4-acetoxy-DMT), also known as O-acetylpsilocin or psilacetin, is a psychedelic drug of the tryptamine family related to psilocybin and psilocin.

[2][5][1] However, it has been said to have reduced side effects such as nausea and body load that can be caused by ingestion of whole psilocybin mushrooms.

[2][1] However, it may technically be a controlled substance under laws throughout the world like the United States's Federal Analogue Act due to its close structural similarity to psilocybin and psilocin.

Despite the preceding reports however, there have been no controlled clinical studies to distinguish the subjective effects of psilacetin, psilocin, and psilocybin.

[2] However, given by intraperitoneal injection at equimolar doses, 4-AcO-DMT showed only 70% of the relative bioavailability or total exposure of psilocybin.

[2] Hence, 4-AcO-DMT results in modestly lower psilocin levels than psilocybin even when the drugs are given at equivalent doses with adjustment for differences in molecular weight.

Given enough time in unfavorable conditions, 4-AcO-DMT can sometimes turn into a degraded form which is brown in color and can even progress into a brown/black tar-like substance.

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.

4-AcO-DMT can be considered an analog of psilocin making it a Schedule 9 prohibited substance in Australia under the Poisons Standard (October 2015).

[22] 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.

[22] 4-AcO-DMT 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.

[citation needed] 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".