Cannabidiol (CBD) for use in the treatment of epilepsy where the epilepsy is a treatment-resistant epilepsy (TRE) and where the CBD is present in an amount that reduces total convulsive seizure frequency by greater than 50% with respect to seizure frequency achieved on concomitant anti-epileptic drugs (AED). The TRE may especially be Dravet syndrome, myoclonic absence seizures, or febrile infection related epilepsy syndrome (FIRES). CBD may be administered in combination with two or more concomitant AEDs, especially clobazam, levetiracetam, topiramate, stiripentol, phenobarbital, lacsamide, valproic acid, zonisamide, perampanel, and fosphenytoin. An especially preferred AED is clobazam (Onfi). Preferably the dose of CBD is from 5 mg/kg/day to 25 mg/kg/day.
