Tetrahydrocannabinol (THC) is a cannabinoid found in cannabis. It is the principal psychoactive constituent of Cannabis and one of at least 113 total cannabinoids identified on the plant. Although the chemical formula for THC (C₂₁H₃₀O₂) describes multiple isomers, the term THC usually refers to the delta-9-THC isomer with chemical name (−)-trans-Δ⁹-tetrahydrocannabinol. It is a colorless oil.

Tetrahydrocannabinol
INN: Dronabinol

Clinical data
Trade names	Marinol, Syndros
Other names	(6aR,10aR)-delta-9-Tetrahydrocannabinol; (−)-trans-Δ9-tetrahydrocannabinol
License data	US FDA: Dronabinol
Dependence liability	Physical: Low Psychological: Low–moderate
Addiction liability	Relatively low: 9%[citation needed]
Routes of administration	By mouth, transdermal, sublingual, inhalation
Drug class	Cannabinoid
ATC code	A04AD10 (WHO)
Legal status
Legal status	AU: Unscheduled: ACT, Schedule 8 (Controlled Drug) BR: Dronabinol: A3; THC <30mg/ml: A3; others: F2 (prohibited). CA: Unscheduled DE: Dronabinol: Anlage III, Δ9-THC: II, other isomers and their stereochemical variants: I. (Does not apply to THC as part of cannabis, which is regulated separately, see Cannabis (drug)) NZ: Class B (medicine form) UK: Class B US: Schedule II as Syndros, Schedule III as Marinol, Schedule I as Δ9-THC in pure form UN: Psychotropic Schedule I /II SE: Förteckning II (Unscheduled when EU-approved industrial hemp <0,3% THC) In general Rx only
Pharmacokinetic data
Bioavailability	Oral: 6–20% Inhalation: 10–35%
Protein binding	97–99%
Metabolism	Mostly hepatic by CYP2C
Metabolites	11-OH-delta-9-THC, and others
Onset of action	Within seconds to minutes when smoked
Elimination half-life	1.6–59 h, 25–36 h (orally administered dronabinol)
Duration of action	2–4 hours when smoked and 4–10 hours when taken orally
Excretion	65–80% (feces) 20–35% (urine) as acid metabolites
Identifiers
IUPAC name (6aR,10aR)-6,6,9-Trimethyl-3-pentyl-6a,7,8,10a-tetrahydro-6H-benzo[c]chromen-1-ol
CAS Number	1972-08-3 Y
PubChem CID	16078
IUPHAR/BPS	2424
DrugBank	DB00470 Y
ChemSpider	15266 Y
UNII	7J8897W37S
KEGG	D00306 Y
ChEBI	CHEBI:66964 N
ChEMBL	ChEMBL465 Y
CompTox Dashboard (EPA)	DTXSID6021327
ECHA InfoCard	100.153.676
Chemical and physical data
Formula	C21H30O2
Molar mass	314.469 g·mol−1
3D model (JSmol)	Interactive image
Specific rotation	−152° (ethanol)
Boiling point	155–157 °C (311–315 °F) 0.05mmHg, 157–160°C @ 0.05mmHg
Solubility in water	0.0028 mg/mL (23 °C)
SMILES CCCCCc1cc(c2c(c1)OC([C@H]3[C@H]2C=C(CC3)C)(C)C)O
InChI InChI=1S/C21H30O2/c1-5-6-7-8-15-12-18(22)20-16-11-14(2)9-10-17(16)21(3,4)23-19(20)13-15/h11-13,16-17,22H,5-10H2,1-4H3/t16-,17-/m1/s1 Y Key:CYQFCXCEBYINGO-IAGOWNOFSA-N Y
NY (what is this?)  (verify)

THC, also known pharmaceutically as dronabinol, is used medically to relieve chemotherapy-induced nausea and HIV/AIDS-related anorexia. Nabiximols, a botanical drug which contains THC, is used medically to treat symptoms of multiple sclerosis, including spasticity and neuropathic pain. THC acts as a partial agonist at CB₁ and CB₂ cannabinoid receptors.

THC can be administered orally, inhaled, or transdermally, with bioavailability and onset varying by route, and is extensively metabolized in the liver to active and inactive metabolites before being excreted in feces and urine. Side effects include red eyes, dry mouth, drowsiness, memory impairment, anxiety, and, with chronic use, cannabinoid hyperemesis syndrome. While human overdose is rare, THC can interact with other drugs and has a complex pharmacokinetic profile.

THC is classified variably under international and US law, with medical use approved in multiple countries. Research supports its effectiveness for spasticity and central pain in multiple sclerosis, though evidence for other neurological disorders is limited, and long-term high-dose exposure may carry uncertain toxicity risks.