4-Acetoxy-N,N-dimethyltryptamine  (also known as 4-AcO-DMT,  4-Acetoxy-DMT,  O-Acetylpsilocin,  and psilacetin)  is a novel psychedelic substance of the tryptamine class.  It is a structural analog of psilocybin,  the active ingredient in psilocybin mushrooms  (magic mushrooms).  Like psilocybin,  it is thought to produce its effects primarily by binding to serotonin receptors in the brain;  however,  the precise mechanism is not fully understood.

The synthesis of 4-AcO-DMT was first reported in 1963 by Albert Hofmann and Franz Troxler as part of an investigation into psilocin analogs.  However, its pharmacology and subjective effects were not explored.  A paper authored by David E. Nichols in 1999 proposed it as a potentially useful alternative to psilocybin for pharmacological research due to lower cost of synthesis.  Reports of recreational use began to surface shortly after its appearance on the online research chemical market in the 2010s.

Subjective effects are reported to be nearly identical to those of psilocybin mushrooms and include geometric visual hallucinations,  time distortion,  enhanced introspection,  euphoria,  and ego loss.  4-AcO-DMT is theorized to act as a prodrug to psilocin in a similar manner as psilocybin,  which may account for this similarity.  4-AcO-DMT’s classical psychedelic effects and favorable tolerability profile has led it to become popular among novel psychoactive substance users who seek mystical or entheogenic experiences.