Higher cannabidiol plasma levels are associated with better seizure response following treatment with a pharmaceutical grade cannabidiol

Abstract Objective The objective of this study was to determine the relationship between cannabidiol (CBD) dose, CBD plasma level, and seizure control in a large open-label single-center study. Methods All participants with treatment-refractory epilepsy participating in our expanded access program (EAP) were approached for participation. Highly purified grade CBD (Epidiolex®) dosing was weight-based and could be increased every 2 weeks by 5 mg/kg/day up to a maximum dosage of 50 mg/kg/day depending on tolerance and seizure control. Seizure counts were obtained at each visit with frequency calculated per 2-week periods. Cross-sectional plasma peak levels of CBD were obtained ~ 4 h after dosing in consecutively presenting patients. Results We evaluated 56 adults and 44 children (100 total; 54 female) at two time points — one before initiating CBD and one at the time of CBD plasma level testing. There was a positive linear correlation between CBD dosage (range from 5 to 50 mg/kg/day) and level (range from 7.1–1200 ng/mL) in all participants (r = 0.640; p  Conclusions In this open-label study, we found evidence of a linear correlation between CBD dosage and plasma levels, and that higher dose/levels are associated with a higher response rate for seizure improvement. Children and adults responded to CBD similarly. However, seizure control response rates suggest children may respond to lower dosages/plasma levels than adults. Findings reported in this study are specific to Epidiolex® and should not be extrapolated to other CBD products.