Rates of full suppression of interictal epileptiform activity were compared for phenobarbital (PHB), carbamazepine (CBZ), and valproate (VPA), in a study at Tufts University School of Medicine, Boston, MA. Comparing 213 pairs of EEGs, overall suppression rates of epileptiform activity in the second EEG were 12/55 (22%) for PHB, 27/81 (33%) for CBZ, and 35/77 (46%) for VPA (P=.005 for VPA vs PHB). Comparing EEG pairs with only generalized or focal discharges, VPA and CBZ were superior to PHB in suppressing generalized interictal epileptiform activity (47%, 38%, and 17%, respectively) and focal discharges (42%, 32%, and 23%, respectively). Comparing EEG pairs whose inter-EEG interval was less than 1 year, VPA and CBZ were equally effective and superior to PHB in suppressing generalized discharges (46%, 50%, and 14%, respectively), whereas VPA was superior to both CBZ and PHB in suppressing focal discharges (40%, 22%, and 19%, respectively). 
COMMENT. Valproate, and to a lesser degree carbamazepine, are superior to phenobarbital in completely suppressing interictal EEG seizure activity in children with epilepsy. Whereas VPA and CBZ are equally effective in controlling generalized discharges, VPA is superior to both CBZ and PHB in suppressing focal EEG discharges, especially when the interval between EEGs is less than 1 year. VPA is also superior to ethosuximide in suppressing generalized epileptiform discharges in children with absence seizures (personal observation).