by determination of primidone and its active metabolites in plasma and brain at 1 , 4 and 12 h after administration of the respective ed50s , it could be shown that unchanged primidone is mostly responsible for the anticonvulsant effect of the first hours , but , at 12 h , only phenobarbital could be detected in both tissues .
C0033148
primidone
C0031412
phenobarbital