Systematic determination of the serum phenytoin level as an aid in the management of children with epilepsy.

The results from systematic determinations of the serum level of phenytoin in 121 epileptic children are reported. The range 12-25 mg/l is effective in most of the children, responding at all to phenytoin, and causes few and minimal side effects. Practically all children with pure grand mal epilepsy could be kept seizure-free on an optimal dose of phenytoin alone. Possibly the level aimed at should be higher in severe cases than in mild ones. Our initial dose was 10 mg/kg daily; this dose was adjusted according to the serum level until the desired range was reached. Phenytoin produced a lower serum level than the same dose of its sodium salt. Interaction possibly occurs with carbamazepine, which tended to decrease the level, and with acetazolamide, which tended to increase the level. With the help of serum phenytoin determinations an individual dose can be chosen for each patient and phenytoin therapy be rendered safer and more effective.