Buy 4-ACO DMT online. 4-AcO-DMT, sometimes referred to as psilocybin or O-acetylpsilocin, is a synthetic hallucinogenic substance that is a member of the tryptamine family. Since it is a legal prodrug for psilocybin in some places, David Nichols has proposed that this acetylated version of the psilocybin mushroom alkaloid, psilocin, could be a potentially helpful substitute for psilocybin in pharmacological research.