[Investigations of serum levels of drugs in children receiving anticonvulsant medication. I. General evaluation of serum concentrations of diphenylhydantoin, primidone and phenobarbitone (author's transl)].

With the aid of our own method of gas chromatography we determined serum concentrations of anticonvulsants in a large number of children who were being treated with diphenylhydantoin, primidone and phenobarbitone. The drugs were being prescribed either as monotherapy, or in combination with each other, or with other substances which have anticonvulsive activity. Regression lines showed good correlations between the quantity of drugs administered (total daily dose) and serum concentrations. The regression lines for diphenylhydantoin and primidone, however, showed no differences, irrespective of whether they were being given alone or in combination. In view of the frequency of symptoms of intoxication and of non-responders, we established a therapeutic range for diphenylhydantoin and primidone (diphenylhydantoin: 5--16 mcg/ml; primidone: 4--14 mcg/ml). The required serum concentrations could be obtained by giving 8--12 mg/kg of diphenylhydantoin, and 15-22 mg/kg of primidone. In spite of the satisfactory correlation between total daily dose and serum concentrations, however, many patients showed departures from this normal behaviour, especially where combination treatments were being conducted. This demonstrates the necessity for routine controls of serum levels.