Δ11-Tetrahydrocannabinol

Δ¹¹-Tetrahydrocannabinol is a rare isomer of tetrahydrocannabinol, developed in the 1970s. It can be synthesized from Δ⁸-THC by several different routes, though only the enantiomer is known.
In recent studies in 2022 it was found to "significantly reduce" the effects of Δ⁹-THC and has been suggested to act as a CB₁ 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 Δ⁹-THC in rhesus monkeys. It has been identified as a component of grey market vaping liquids sold for use in humans. Δ¹¹-THC has been identified as an impurity found in pharmaceutical dronabinol.

Legality

United States

As of now, Δ¹¹-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, Δ¹¹-THC, being an isomer and analogue of illicit Δ⁹-THC means it can be persecuted under the Federal Analogue Act.

Arkansas

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 Δ¹¹-THC. This ruling means that Act 629, which classifies delta-8, delta-9, and delta-10 THC as Schedule VI controlled substances in the state, is now enforceable. Previously, sales of these products had been temporarily permitted due to the injunction.

Japan

Δ¹¹-THC falls under general THC restriction in Japan and is illegal to possess or use.