Primidone, Serum or Plasma

This deoxybarbiturate is closely related chemically to the barbiturates. It is converted to two active metabolites, phenobarbital and phenylethylmalonamide (PEMA). Primidone is used principally in generalized tonic-clonic and complex and simple partial seizures; some clinicians believe that the drug has specific usefulness for complex partial seizures. It is as effective as carbamazepine or phenytoin in controlling partial or generalized tonic-clonic seizures, although a greater incidence of adverse reactions, especially during initial therapy, limits patient acceptance. Primidone is commonly given with phenytoin but monotherapy is preferred. The conversion of primidone to phenobarbital is significantly increased when this drug is used with other antiepileptic medication. It is not effective in absence seizures.