Placebo-controlled study of phenobarbitone and phenytoin in the prophylaxis of febrile convulsions.

Of 138 children who had a first febrile convulsion before their second birthday, 48 were treated with phenobarbitone, 47 with phenytoin, and 43 with a placebo for 12 months. Drug levels were monitored and adverse effects of the drugs were noted. Compared with placebo, phenobarbitone significantly reduced recurrences among children under 14 months old at the time of their first convulsion, but nor among older children. Phenytoin was an ineffective prophylactic agent. Ideal drug levels were difficult to maintain, and many recurrences occurred when concentrations were suboptimal. Behavioural disturbance in children taking phenobarbitone was not a serious problem. The decision to give continuous prophylaxis for febrile convulsions is complex, and each case must be judged on its merits. For children who have a first seizure before 14 months of age prophylaxis may be advisable and phenobarbitone is effective.