Tetrahydro­cannabinol

What it isDelta-9-tetrahydrocannabinol, the principal psychoactive constituent of cannabis and a partial agonist at CB1 and CB2 receptors.

Why this oneIt is the molecule behind cannabis's intoxicating, appetite-stimulating and antiemetic effects, and the reference point against which every cannabinoid — including the non-intoxicating cannabidiol — is described.

What limits itCB1 agonism in the CNS brings tachycardia, anxiety and psychosis risk, impaired driving, and cannabinoid hyperemesis with heavy chronic use; it is a CYP3A4 and CYP2C9 substrate, so interactions track those enzymes.