Early research indicates that cannabidiol (CBD), a non-psychoactive compound derived from marijuana, may have the potential to prevent or treat COVID-19. Several recent laboratory studies have shown promising results, attracting media attention and sparking interest in further clinical trials.
Marsha Rosner of the University of Chicago led a team that found CBD appeared to help curb SARS-CoV-2 in infected cells in laboratory experiments. According to their findings published in Science Advances, small doses of highly purified CBD, similar to those used in an approved oral drug for severe epilepsy, did not prevent the virus from infecting cells. Instead, CBD acted after the virus entered the cells, blocking its replication, partly through effects on the inflammatory protein interferon. Similar effects were observed in infected mice.
When the researchers examined a group of adults with severe epilepsy, they found that those taking the approved CBD drug had lower rates of COVID-19. However, Rosner cautioned that this retrospective observation is not conclusive and that only randomized clinical trials can provide definitive evidence.
Other Cannabinoids
Interestingly, small doses of tetrahydrocannabinol (THC), the psychoactive component of marijuana, as well as cannabidiolic acid (CBDA), cannabidivarin (CBDV), cannabichromene (CBC), and cannabigerol (CBG), did not prevent the virus from entering cells or stop it from replicating. Rosner noted that combining THC with CBD even negated CBD's effects.
A separate team reported in the Journal of Natural Products that high doses of CBG and CBDA could prevent the coronavirus from entering cells. Richard van Breemen from Oregon State University stated that the doses tested were non-toxic to cells. However, the safety of such high doses in humans remains unclear.
Dosage and Purity Concerns
Rosner emphasized the importance of using the lowest effective dose of CBD due to potential side effects as the drug is processed by the liver. The CBD used in her team's experiments was more than 98% pure, while commercial products often have lower purity levels. She cautioned against using CBD products from dispensaries without proper clinical evidence.
Ongoing Clinical Trials
Several small CBD trials in humans with COVID-19 are currently underway. In one completed study in Brazil, 105 patients with mild or moderate COVID-19 were randomly assigned to receive CBD or a placebo for 14 days along with standard care. The results, published in Cannabis and Cannabinoid Research, showed no apparent effect of CBD.
A proof-of-concept study at Sheba Medical Center in Israel is randomly assigning patients with mild COVID-19 to receive CBD or a placebo. Additionally, an early-stage trial at Rabin Medical Center, also in Israel, aims to test the effect of CBD in severely or critically ill patients. However, the study leader, Dr. Moshe Yeshurun, noted that enrolling participants has been challenging due to the current Omicron-driven wave, which primarily consists of patients with mild to moderate disease.
Rosner's team is considering a clinical trial focusing on asymptomatic or mild cases of COVID-19. She expressed concern that media reports overstating the potential of cannabinoids could lead people to self-medicate with CBD, stop using masks, and avoid vaccines. She emphasized that vaccine-induced antibodies and antibody drugs are currently much more effective at blocking infection.
