Epidiolex may cause seizures, other side effects in rare cases: Study

Safety study finds potential new side effects not previously listed

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Epidiolex (cannabidiol), an approved treatment for seizures in Dravet syndrome, may in some rare cases cause side effects including clusters of seizures, vision impairment, and problems with speech.

That’s according to a new study, “Adverse Events of Epidiolex: A Real-world Drug Safety Surveillance Study based on the FDA Adverse Event Reporting System (FAERS) Database,” which was published in the Asian Journal of Psychiatry.

“We found that real-world adverse reactions largely align with those in Epidiolex’s drug leaflet,” the researchers wrote.

However, “seizure cluster” and several other adverse events “emerged as potential new side effects not previously listed, warranting further attention for drug safety,” the team wrote.

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Epidiolex is an oral formulation of cannabidiol, known as CBD, that’s approved in the U.S. to help manage seizures in people with Dravet or Lennox-Gastaut syndrome, another condition characterized by childhood seizures.

The therapy — a plant-derived cannabidiol, a non-psychoactive marijuana extract — is now indicated in the U.S. for patients ages 1 or older with these conditions.

Like any medication, Epidiolex can cause adverse events. Common side effects reported in Epidiolex clinical trials included sleepiness, fatigue, sleep problems, reduced appetite, diarrhea, rash, infection, and increased liver enzymes, which are a sign of liver damage.

Now, scientists in China conducted an in-depth analysis of safety data for Epidiolex collected using the U.S. Food and Drug Administration’s Adverse Event Reporting System database. The data spanned from 2018, when the therapy was first approved in the U.S., through early 2023.

During that roughly five-year period, a total of 13,275 safety-related issues were reported for patients on Epidiolex, according to the researchers.

The scientists combed through these reports, looking for events that showed signs of being a direct side effect of Epidiolex — as opposed to a coincidental medical issue.

The team found many events that were in line with the known safety profile of the medication; for example, diarrhea and sleepiness were frequently reported. But they also noted a few potential side effects that have not been previously reported with Epidiolex.

There were 81 cases in which patients given Epidiolex experienced cluster seizures, where two or more seizures occur within 24 hours of each other.

The researchers speculated that this may be a result of Epidiolex acting on the brain or interacting with other seizure-controlling medications in ways that aren’t yet fully appreciated.

Differences in dosing of the therapy also may play a role, the researchers said, adding that, “a slower, more individualized approach to dosing, along with vigilant monitoring for adverse events, could help optimize the risk-benefit profile of Epidiolex for patients.”

[These results] may suggest risks that physicians need to pay particular attention to when using Epidiolex, especially when similar symptoms are observed in patients.

Besides seizure clusters, there also were a handful of cases of other previously-unreported side effects, which included cortical visual impairment, or problems with vision due to dysregulation of the parts of the brain responsible for interpreting signals from the eyes.

Other side effects were overactive throat reflexes and reduced speech. A few patients also showed potentially drug-related changes in levels of blood ketones, a marker of fat metabolism.

Overall, these results “may suggest risks that physicians need to pay particular attention to when using Epidiolex, especially when similar symptoms are observed in patients,” the team wrote.