O-Acetylpsilocin (also known as psilacetin, 4-acetoxy-DMT, or 4-AcO-DMT) 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. However, some users report that O-acetylpsilocin's subjective effects differ from those of psilocybin and psilocin. 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.