Psilocybin

Psilocybin
INN: Psilocybine
	Skeletal formula of canonical psilocybin
	Ball-and-stick model of canonical psilocybin
Clinical data
Pronunciation	/ˌsaɪləˈsaɪbɪn/ sy-lə-SY-bin, /ˌsɪl-/
Other names	Psilocybine; Psilocibin; Psylocybin; Psilotsibin; Psilocin phosphate; Psilocin phosphate ester; O-Phosphorylpsilocin; O-Phosphoryl-4-hydroxy-N,N-dimethyltryptamine; 4-Phosphoryloxy-N,N-dimethyltryptamine; 4-PO-DMT; COMP360; COMP-360; CY-39; CY39; PSOP, Psilocybin (USAN US)
Dependence; liability	Low
Addiction; liability	Low
Routes of; administration	By mouth,; intravenous;
Drug class	Serotonergic psychedelic; Hallucinogen; Serotonin receptor agonist; Serotonin 5-HT2A receptor agonist
ATC code	None;
Legal status
Legal status	AU: S9/S8 (Controlled Drug); BR: Class F2 (Prohibited psychotropics); CA: Schedule III; UK: Class A; US: Schedule I;
Pharmacokinetic data
Bioavailability	Oral: 52.7 ± 20.4% (as psilocin) (n=3)
Protein binding	66%
Metabolism	Liver, other tissues:; • Dephosphorylation (ALPTooltip alkaline phosphatase); • Demethylation and deamination (MAOTooltip monoamine oxidase); • Oxidation (ALDHTooltip aldehyde dehydrogenase); • Glucuronidation (UGTs)
Metabolites	• Psilocin; • Psilocin-O-glucuronide; • 4-Hydroxyindole-3-acetaldehyde; • 4-Hydroxyindole-3-acetic acid (4-HIAA); • 4-Hydroxytryptophol
Onset of action	Oral: 0.5–0.8 (range 0.1–1.5) h; IVTooltip Intravenous injection: immediate
Elimination half-life	Oral (as psilocin): 2.1–4.7 h (range 1.2–18.6 h); IVTooltip Intravenous administration (as psilocin): 1.2 h (range 1.8–4.5 h)
Duration of action	Oral: 4–6 h (range 3–12 h); IVTooltip Intravenous injection: 15–60 min (1–2 mg)
Excretion	urine (mainly as psilocin-O-glucuronide, 2–4% as unchanged psilocin)
Identifiers
	IUPAC name [3-[2-(dimethylamino)ethyl]-1H-indol-4-yl] dihydrogen phosphate;
CAS Number	520-52-5 ;
PubChem CID	10624;
DrugBank	DB11664;
ChemSpider	10178 ;
UNII	2RV7212BP0;
KEGG	D12881 ;
ChEBI	CHEBI:8614 ;
ChEMBL	ChEMBL194378 ;
CompTox Dashboard (EPA)	DTXSID0048898 ;
ECHA InfoCard	100.007.542
Chemical and physical data
Formula	C12H17N2O4P
Molar mass	284.252 g·mol−1
3D model (JSmol)	Interactive image;
Melting point	220–228 °C (428–442 °F)
	SMILES CN(C)CCC1=CNC2=C1C(=CC=C2)OP(=O)(O)O;
	InChI InChI=1S/C12H17N2O4P/c1-14(2)7-6-9-8-13-10-4-3-5-11(12(9)10)18-19(15,16)17/h3-5,8,13H,6-7H2,1-2H3,(H2,15,16,17) ; Key:QVDSEJDULKLHCG-UHFFFAOYSA-N ;
	(verify)

Psilocybin, also known as 4-phosphoryloxy-N,N-dimethyltryptamine (4-PO-DMT), is a naturally occurring tryptamine alkaloid and investigational drug found in more than 200 species of mushrooms, with hallucinogenic and serotonergic effects. Effects include euphoria, changes in perception, a distorted sense of time, and perceived spiritual experiences.

Psilocin is the metabolite of psilocybin. The compound psilocybin itself is biologically inactive but quickly converted by the body to psilocin. Psilocybin is transformed into psilocin by dephosphorylation mediated via phosphatase enzymes. Psilocin is chemically related to the neurotransmitter serotonin and acts as a non-selective agonist of the serotonin receptors. Activation of one serotonin receptor, the serotonin 5-HT_2A receptor, is specifically responsible for the hallucinogenic effects of psilocin and other serotonergic psychedelics. Psilocybin is usually taken orally. By this route, its onset is about 20 to 50 minutes, peak effects occur in about 1 to 2 hours, and its duration is about 4 to 6 hours.

Psilocybin mushrooms were used ritualistically in pre-Columbian Mexico, but claims of their widespread ancient use are largely exaggerated and shaped by modern idealization and ideology. In 1958, the Swiss chemist Albert Hofmann isolated psilocybin and psilocin from the mushroom Psilocybe mexicana. His employer, Sandoz, marketed and sold pure psilocybin to physicians and clinicians worldwide for use in psychedelic therapy. Increasingly restrictive drug laws of the 1960s and the 1970s curbed scientific research into the effects of psilocybin and other hallucinogens, but its popularity as an entheogen grew in the next decade, owing largely to the increased availability of information on how to cultivate psilocybin mushrooms. Possession of psilocybin-containing mushrooms has been outlawed in most countries, and psilocybin is classified as a Schedule I controlled substance in the 1971 United Nations Convention on Psychotropic Substances.

Psilocybin is being studied as a possible medicine in the treatment of psychiatric disorders such as major depressive disorder, substance use disorders, obsessive–compulsive disorder, and other conditions such as cluster headaches. Psilocybin was approved for treatment-resistant depression in Australia in 2023. It is in late-stage clinical trials in the United States for major depressive disorder and treatment-resistant depression. As of September 2026, complete submission of psilocybin for treatment-resistant depression is expected in the fourth quarter of 2026 and commercial launch for this indication is anticipated in the first half of 2027. Especially at higher doses and combined with psychological support, single doses of psilocybin may produce rapid and long-lasting antidepressant effects that outperform placebo, though they may produce either modest or no effectiveness advantage over continuous use of selective serotonin reuptake inhibitors (SSRIs) like escitalopram and trial methodological issues are common. It can cause adverse reactions such as nausea and panic attacks.