New research in the journal Epilepsia suggests that cannabidiol (CBD) may interact negatively with commonly used antiepileptic drugs (AEDs). In the ongoing, open-label compassionate-use study, 42 adults and 39 children received CBD in addition to their epilepsy treatment. According to results for the full group, an increasing dose of CBD was linked with increases in serum levels of rufinamide, topiramate, and N-desmethylclobazam and a decrease in clobazam. In a subgroup of only adults, there was a significant association between increasing CBD dose and higher zonisamide and eslicarbazepine serum levels. With the exception of N-desmethylclobazam/clobazam, all of the serum-level changes were considered to be within the accepted therapeutic range. The researchers noted, however, that increasing CBD dosing was associated with changes on liver function tests for the full study group receiving concomitant valproate. The findings underline the necessity of monitoring AED levels and liver tests when treating with CBD, said lead author Tyler E. Gaston, MD, assistant professor of neurology at the University of Alabama at Birmingham Epilepsy Center. Further research is needed to confirm the findings, Gaston said.