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A case study of 19 individuals with drug-resistant epilepsy who used cannabis oil found that the median duration of seizure freedom after starting treatment was 245 days. Five patients remained continuously seizure-free for more than a year. The study was published in Frontiers in Neuroscience.
Epilepsy is a chronic neurological disorder marked by recurrent, unprovoked seizures caused by abnormal electrical activity in the brain. It can result from genetic factors, brain injury, infections, or sometimes for reasons that remain unknown. Seizures vary widely in type and severity, ranging from brief lapses in attention to full-body convulsions.
Treatment typically involves anti-seizure medications, which help most people manage their seizures effectively. Some individuals also benefit from dietary therapy, nerve stimulation, or surgery.
However, for a significant minority, standard treatments fail to adequately control seizures. When seizures persist despite at least two appropriately chosen and adequately trialed anti-seizure medications, the condition is classified as drug-resistant epilepsy.
Study author Frank Yizhao Chen and his colleagues conducted a retrospective case series examining seizure outcomes after patients with drug-resistant epilepsy began treatment with cannabis-based medicinal products in oil form.
The study included 19 individuals selected from a pool of 174 patients with drug-resistant epilepsy. All were treated at North Toronto Neurology, an outpatient neurology clinic in Toronto, Canada, through the clinic’s Medical Cannabis Program. Each patient received authorization for medical cannabis use from the program’s neurologist.
The program begins with an educational session and initial consultation. If the patient is deemed medically suitable—meaning they do not have unstable cardiac, renal, hepatic, or psychiatric conditions—they are authorized to use cannabis oils in accordance with Canadian medical cannabis regulations.
The treatment protocol consists of five phases. It begins with cannabidiol (CBD)-only oils, with doses gradually increased until either seizure control is achieved or side effects become problematic. If CBD alone does not lead to sufficient improvement, delta-9-tetrahydrocannabinol (THC) is added while reducing the CBD dose. Patients are monitored regularly, and treatment is adjusted based on seizure response.
Researchers tracked seizure frequency before, during, and after cannabis oil treatment using patient- or caregiver-reported logs. Standardized seizure calendars were not used.
Results showed that 11 patients achieved seizure freedom without requiring changes to their initial cannabis oil regimen. An additional 7 patients became seizure-free within one week of starting treatment. Four patients required the addition of THC to their CBD-only regimen to achieve seizure control.
The median duration of each patient’s first seizure-free period was 211 days, with a range of 90 to 412 days. In total, the median cumulative seizure-free duration across patients was 245 days. Five patients achieved seizure freedom for at least one year.
Five patients were treated with CBD alone, while the remaining 14 used a combination of CBD and THC. The median CBD dose for the CBD-only group was 6.8 mg/kg/day, while those using both CBD and THC received a median CBD dose of 7.58 mg/kg/day. The median THC dose was 0.31 mg/kg/day.
Overall, 90% of patients reported improvements in quality of life. Among patients who were not continuously seizure-free but remained on cannabis oil, their monthly seizure frequency dropped by 69% compared to baseline.
“The results of the study support prioritizing CBPMs [cannabis-based products for medicinal use] in cases of DRE [drug-resistant epilepsy]. It also supports research into identifying clinical and biological biomarkers for DRE cases that may achieve SF [seizure freedom] under CBPM treatment. Lastly, the study supports improving the accessibility of CBPMs, using SF as a primary outcome in future CBPM epilepsy trials, and assessing the role of THC in reducing seizures,” the authors concluded.
The study highlights the potential of cannabis-based medicinal products to induce long-term seizure freedom in some individuals with drug-resistant epilepsy. However, it is important to note that this was not a controlled experimental study. There was no placebo group or blinding, and the findings rely on observational data. As such, it cannot be confirmed that the observed improvements were solely due to the cannabis treatment.
The paper, “19 patients report seizure freedom with medical cannabis oil treatment for drug-resistant epilepsy: a case series,” was authored by Frank Yizhao Chen, Joshua Myles Duckman, Brenden Samuel Rabinovitch, Katrin Julia Hannesson, and Evan Cole Lewis.
