Introduction: Cannabidiol (CBD) has antiseizure properties but no psychoactive effects. Randomized controlled trials of an oral, pharmaceutical formulation of highly purified CBD are promising; however, data regarding other formulations are sparse and anecdotal. We evaluated the effectiveness of add-on therapy with a standardized CBD-based oil in treatment-resistant epilepsy (TRE) patients.
Materials and Methods: An open retrospective study was carried out on patients with refractory epilepsy of different etiology. We reviewed clinical data from medical charts and caregiver’s information. Participants received add-on with 24% CBD-based oil, sublingually administered, at the starting dose of 5–10 mg/[kg·day] up to the maximum dose of 50 mg/[kg·day], based on clinical efficacy. Efficacy was evaluated based on patients being seizure free or experiencing at ≥50% improvement on seizure frequency. Tolerability and suspected adverse drug reaction data were also analyzed.
Results: We included 37 patients (46% female) with a median age of 16.1 (range: 2–54) years. Twenty-two (60%) patients suffered from epileptic encephalopathy, 9 (24%) from focal epilepsy, and 6 (16%) from generalized epilepsy. Mean follow-up duration was 68 (range: 24–72) weeks. The average age at seizure onset was 3.8±2.1 years (range: 7 days–21 years). The median achieved CBD-based oil dose was 4.2±11.4 (range: 0.6–50) mg/[kg·day]. At 40-month follow-up, 7 (19%) patients were seizure free, 27 (73%) reported >50% improvement, 2 (5%) patients reported <50% improvement, and 1 patient discontinued therapy due to lack of efficacy. Weaning from concomitant antiepileptic drugs was obtained after 24 weeks from CBD introduction in 10 subjects. Mild and transitory adverse events, including somnolence or loss of appetite, occurred in nine (25%) patients. Discussion and Conclusion: We showed the efficacy of a CBD-based oil formulation with few significant side effects in patients with TRE of various etiologies.