This study was published in December 2022 in the journal Epilepsia. It examined CBD isolate as an add-on treatment in patients suffering from treatment resistant epilespy (TRE). It's also called intractable, refractory, uncontrolled or drug-resistant Epilepsy. It is a condition where standard pharmaceutical medicines do not work well to control seizures and convulsions.
The participants used a highly purified form of CBD isolate (Epidiolex®; 100 mg/ml oral solution), increasing the dose from 2 to 10 mg/kg/day to tolerance or maximum 25–50 mg/kg/day dose. 10mg/kg/day = 700mg CBD per day per 154 lb. (70kg) person. 50mg/kg/day = 3500mg CBD per day per 154 lb. person. These fairly large doses of CBD were an add-on to other epilepsy medications.
Data was collected between 2014 and 2019, and spans 192 weeks of patient tracking at 12 week intervals. The most common additional drugs used in conjunction with CBD were clobazam (47%), levetiracetam (34%), and valproate (28%).
They started with 892 patients and 36% eventually withdrew. 19% withdrew because of lack of efficacy (it didn't help). 7% experienced adverse effects (AEs) and withdrew. For the remaining patients, it did work:
Median percentage reduction from baseline ranged 50%–67% for convulsive seizures and 46%–66% for total seizures.
Median top CBD dose was 25 mg/kg/day [1750mg per day per 154 lb. person]; median exposure duration was 694 days.
So for the patients that completed the study, their seizures were reduced by about one-half to two-thirds over a period of almost 2 years.
The most common AEs were diarrhea, seizure, and somnolence. The majority of patients reported at least one AE.
The authors' conclusion:
Add-on CBD was associated with sustained seizure reduction up to 192 weeks with an acceptable safety profile and can be used for long-term treatment of TREs.
The abstract is available here at the Wiley Online Library.