A Comparison of Phenobarbital and Phenytoin Serum Levels between Children with Status Epilepsy and Refractory Status Epilepsy.

Background & Objective: Due to high kinetic variation of antiepileptic medications in children, judgment on the efficacy of intravenous phenytoin and phenobarbital in treatment of refractory status epilepsy, requires measurement of serum levels of the drugs. The aim of this study was determine and compare serum levels of phenytoin and phenobarbital, as the two major and common first- line drugs in treatment of children with status epilepsy and refractory status epilepsy. Materials & Methods: Serum levels of phenytoin and phenobarbital in ۲۰ children (۱month – ۱۲years) with refractory status epilepsy (candidates for midazolam infusion) was compared with ۲۰ children with status epilepsy. Age, gender, etiology, type of seizure and previous use of antiepileptic drugs were matched. Results: In patients with status epilepsy and refractory status epilepsy mean serum levels of phenobarbital were ۲۸.۰۳ ± ۱۲.۷ µg/ml, ۳۷.۲۲ ± ۲۰.۷۸ µg/ml respectively while serum levels of phenytoin were ۳۰.۳۸ ± ۱۶.۸۰ µg/ml, ۳۱.۴۲ ± ۱۴.۸۱ µg/ml respectively. There was no significant difference between phenobarbital (P=۰.۱) and phenytoin (P=۰.۸) serum levels in these two groups. There was no significant correlation between phenobarbital serum level with age in the group of status epilepsy (P=۰.۱) and refractory status epilepsy (P=۰.۸). In contrast, increased phenytoin serum level was associated with increased age in status epilepsy group (P=۰.۰۰۴) and refractory status epilepsy group (P=۰.۰۱). In both groups, blood level of the drugs were within the therapeutic range. Conclusion: High pharmacokinetic variation of antiepileptic medications in children does not cause any changes in the serum level of intravenous phenytoin and phenobarbital in the groups of status epilepsy and refractory status epilepsy. Development of refractory status epilepsy is probably due to the nature of disease or other unknown factors which need further studies.

Keywords:

Status epilepsy , Refractory status epilepsy , Phenobarbital , Phenytoin