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A Second Look At Epidiolex: Does It Actually Work?

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Written by Alexandra Hicks

Epidiolex is the first and only CBD-based medication to receive FDA approval in the United States, but a recent study suggests it may not be as effective as everyone believed.

Epidiolex was approved in 2018 following three randomized, double-blind, placebo-controlled clinical trials, involving 516 patients with one of two rare seizure disorders: Lennox-Gastaut or Dravet syndrome. However, this new study, published in the British Journal of Clinical Pharmacology, claim that the reduction in seizures attributed to Epidiolex might actually be the result of Clobazam, a drug that’s already used to treat epilepsy.

After taking a second look at the research, it seems that many patients from the trial were also taking Clobazam. “I was flabbergasted when I saw that 50 percent in one study and 60 percent in the other study were actually using this other drug, said Geert Jan Groeneveld in an interview with Analytical Cannabis, the chief scientific officer at the Centre for Human Drug Research in the Netherlands, and lead author of the new study.


According to some documentation, all three of the FDA-cited studies gave the study participants Clobazam to take “concomitantly” with cannabidiol. It’s strange though, that if this what the basis of the research the entire time, why was Epidiolex being prescribed as a stand-alone medication until now?

Now, Groenveld and his colleagues are now calling the effects of just CBD into question. “I’m not saying that I know for a fact that cannabidiol does not have any anti-epileptic effects,” Groeneveld said. “What I am saying is, I can explain the effects that you’ve observed through elevated blood levels of clobazam.”

During their study, Groeneveld and his team replicated the original FDA-trials under the assumption that blood-clobazam levels were around 10 to 20 mg for each participant. They discovered that the drugs work well together and the combination could be better than using each drug individually, however, more research is needed to confirm this.

“[If GW] haven’t shared [the clobazam data] with the FDA, and Epidiolex has been approved in that case, I think it should lead to reassessing whether that was done correctly and whether Epidiolex should be approved for the treatment of epilepsy,” Groeneveld added

Epidiolex was recently approved for research in Japan and use in Europe, so check back with us for more updates. 

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About the author

Alexandra Hicks

Managing editor at Cannadelics and U.S based journalist, helping spread the word about the many benefits of using cannabis and psychedelics.