Efficacy of cannabidiol in subjects with refractory epilepsy relative to concomitant use of clobazam.

OBJECTIVE: To evaluate the efficacy of open-label, highly purified cannabidiol (CBD, Epidiolex®) in treating refractory epilepsy relative to the concomitant use of clobazam (CLB) as well as the clinical implications of changes in CLB and norclobazam (nCLB) levels. METHODS: Data were examined retrospectively, in patients who either used CBD with concomitant CLB or without concomitant CLB after two months of treatment with CBD and at the point of best seizure control within the first year of treatment with CBD. Responder rates (percentage of subjects with a 50 % or greater reduction in weekly seizures from their baseline) and mean reduction in weekly seizure frequency were calculated and compared between those who concomitantly used CLB and those who did not. The relationship between the change in CLB and nCLB levels and change in mean weekly seizure frequency was also investigated within the group of subjects using concomitant CLB and CBD. RESULTS: We analyzed data from 47 subjects between the ages of 2.5-51 years. There was no significant difference between the concomitant CLB (n = 32) and no concomitant CLB (n = 15) groups in terms of demographics (age (p = 0.4344), race (p = 1.0000), sex (p = 0.7507)) or most epilepsy characteristics (underlying condition (all p > 0.05), mean baseline seizure frequency (p = 0.6483)). There was only one significant difference between groups regarding seizure types (more subjects with epileptic spasms in concomitant CLB group (p = 0.0413)). Concomitant AED usage was not significantly different in the two groups (all p > 0.05). Mean reduction in weekly seizure frequency was greater at the best point of seizure control within the first year than at two months of treatment with CBD, regardless of concomitant CLB usage (all p > 0.05). There was no significant difference in reduction of mean weekly seizure frequency between those who took concomitant CLB and those who did not at either time point (all p > 0.05). There was a significantly greater responder rate for subjects taking CBD and CLB than those taking CBD without CLB only at the point of best seizure control within the first year of CBD treatment (p = 0.0240). There was no strong, significant correlation between change in nCLB or CLB levels and change in seizure frequency at either time point (all |p|<0.22). SIGNIFICANCE: With or without concomitant CLB, CBD can be effective in reducing seizure frequency. Changes in nCLB and CLB levels do not have a clinically significant correlation with changes in weekly seizure frequency for those taking CBD with CLB.