In humans as well as other mammals, psilocybin is transformed into the active metabolite
psilocin, or 4-hydroxy-N,N-dimethyltryptamine (C12H16N2O.) It is likely that psilocin partially or
wholly produces most of the subjective and physiological effects of psilocybin in humans and
nonhuman animals.
Psilocybin is detectable in plasma 20 to 40 minutes after oral administration (Hasler 1997) reviewed in (Passie et al. 2002). Psilocybin is metabolized in the liver, where it is chiefly transformed into the active metabolite psilocin, detectable in plasma 30 minutes after administration (Hasler 1997; Hasler et al. 1997; Lindenblatt et al. 1998; Passie et al.2002), with psilocin first appearing in plasma 15 to 50 minutes after oral administration of 0.2 mg/kg psilocybin.