11-Hydroxy-THC

11-Hydroxy-Δ9-tetrahydrocannabinol (11-OH-Δ9-THC, alternatively numbered as 7-OH-Δ1-THC), usually referred to as 11-hydroxy-THC is the main active metabolite of tetrahydrocannabinol (THC), which is formed in the body after Δ9-THC is consumed.

After cannabis consumption, THC is metabolized inside the body by cytochrome P450 enzymes such as CYP2C9 and CYP3A4 into 11-hydroxy-THC and then further metabolized by dehydrogenase and CYP2C9 enzymes to form 11-nor-9-carboxy-THC (THC-COOH) which is inactive at the CB1 receptors; and further glucuronidated to form 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid glucuronide (Δ9-THC-COOH-glu) in the liver, from where it is subsequently excreted through feces and urine (via bile from the liver). Both metabolites, along with THC, can be assayed in drug tests.

11-hydroxy-THC can be formed after consumption of THC from inhalation (vaping, smoking) and oral (by mouth, edible, sublingual) use, although levels of 11-hydroxy-THC are typically higher when eaten compared to inhalation.

Pharmacology
Like Δ9-THC, 11-hydroxy-THC is a partial agonist at the cannabinoid receptor CB1, but with significantly higher binding affinity (Ki = 0.37 nM compared to Δ9-THC Ki = 35 nM). With respect to cAMP inhibition at CB1 it displays a similar efficacy to that of Δ9-THC (EC50 = 11 nM vs. EC50 = 5.2 nM, respectively), but a lower maximum response (Emax = 28% vs. Emax = 70%).

Research
In an in vitro analysis by the University of Rhode Island on cannabinoids it was found that 11-OH-Δ9-THC had the 3rd highest 3C-like protease inhibitor activity against COVID-19 out of all the cannabinoids tested within that study but not as high as the antiviral drug GC376 (56% for 11-OH-Δ9-THC vs. 100% for GC376).