ÃÂ<sup>11</sup>-Tetrahydrocannabinol (delta-11-THC, exo-THC, ÃÂ<sup>11</sup>-THC, ÃÂ<sup>9(11)</sup>-THC, exo-tetrahydrocannabinol) is a rare isomer of tetrahydrocannabinol (ÃÂ<sup>9</sup>-THC), developed in the 1970s. It can be synthesized from ÃÂ<sup>8</sup>-THC by several different routes, though only the (6aR, 10aR) enantiomer is known.
In recent studies in 2022 it was found to "significantly reduce" the effects of ÃÂ<sup>9</sup>-THC and has been suggested to act as a CB<sub>1</sub> receptor antagonist in humans, with the cited study showing "one partial success in the quest for an antagonist is the fact that D9,11-THC was found to significantly reduce the effect of D9-THC" and did not substitute for ÃÂ<sup>9</sup>-THC in rhesus monkeys. It has been identified as a component of grey market vaping liquids sold for use in humans. ÃÂ<sup>11</sup>-THC has been identified as an impurity found in pharmaceutical dronabinol.
As of now, ÃÂ<sup>11</sup>-THC is federally legal and uncontrolled, and faces no repercussions for possession unless in Arkansas or other states that prohibit intoxicating hemp-derived cannabinoids. However, ÃÂ<sup>11</sup>-THC, being an isomer and analogue of illicit ÃÂ<sup>9</sup>-THC means it can be persecuted under the Federal Analogue Act.
As of 25 June 2025, the U.S. 8th Circuit Court of Appeals overturned a lower court's injunction, allowing Arkansas to enforce its ban on hemp-derived THC products, including ÃÂ<sup>11</sup>-THC. This ruling means that Act 629, which classifies delta-8, delta-9 (above 0.3%), and delta-10 THC ("Psychoactive hemp-derived cannabinoids" as stated in Act 629) as Schedule VI controlled substances in the state, is now enforceable. Previously, sales of these products had been temporarily permitted due to the injunction.
ÃÂ<sup>11</sup>-THC falls under general THC restriction in Japan and is illegal to possess or use.