Withdrawal of barbiturate anticonvulsant drugs: prospective controlled study.

A barbiturate (phenobarbital or primidone) was withdrawn over a period of 3 months from 25 institutionalized residents, all of whom had had three seizures or less in the past 6 months and were maintained on a nonsedating drug (phenytoin, carbamazepine, or valproic acid). Results were compared with a matched comparison group maintained on both drugs. Subjects withdrawn from primidone, but not those withdrawn from phenobarbital, had increased seizure frequency, probably due to withdrawal. After 14 months, seizure-free subjects withdrawn from barbiturates were no more likely to have had seizures than were comparison subjects. Barbiturates appear to be unnecessary and may be withdrawn.