Review of delta‐8‐tetrahydrocannabinol (Δ<sup>8</sup>‐THC): Comparative pharmacology with Δ<sup>9</sup>‐THC
Michael Tagen, Linda E. Klumpers
Abstract
The use of the intoxicating cannabinoid delta‐8‐tetrahydrocannabinol (Δ 8 ‐THC) has grown rapidly over the last several years. There have been dozens of Δ 8 ‐THC studies dating back over many decades, yet no review articles have comprehensively covered these findings. In this review, we summarize the pharmacological studies of Δ 8 ‐THC, including receptor binding, cell signalling, in vivo cannabimimetic activity, clinical activity and pharmacokinetics. We give special focus to studies that directly compared Δ 8 ‐THC to its more commonly studied isomer, Δ 9 ‐THC. Overall, the pharmacokinetics and pharmacodynamics of Δ 8 ‐THC and Δ 9 ‐THC are very similar. Δ 8 ‐THC is a partial agonist of the cannabinoid CB 1 receptor and has cannabimimetic activity in both animals and humans. The reduced potency of Δ 8 ‐THC in clinical studies compared with Δ 9 ‐THC can be explained by weaker cannabinoid CB 1 receptor affinity, although there are other plausible mechanisms that may contribute. We highlight the gaps in our knowledge of Δ 8 ‐THC pharmacology where further studies are needed, particularly in humans.