Prophylaxis against febrile convulsions with phenobarbital. A 3-year prospective investigation.

An unselected patient material of 182 children admitted consecutively with febrile convulsions during a period of two years was classified into five risk-groups. Continuous phenobarbital therapy for two years was recommended for 113 children (Groups I--IV). These children were followed-up as out-patients for at least one year after admission. In children receiving phenobarbital therapy, serum concentrations were controlled every third month. A total of 59 children completed the treatment according to the directives given and seven of these (12%) developed renewed febrile convulsions despite serum phenobarbital concentrations within the therapeutic range (70--120 mumol/l). No particular characteristics for these children could be established on the basis of the parameters registered. The therapeutic model established was found to be suitable for distinguishing between children with massive risk for renewed convulsions (Group I--IV) compared with children for whom treatment was not recommended (Group V).