Disappearance of phenobarbital and diphenylhydantoin from serum of children

Children were treated for epilepsy with phenobarbital and diphenylhydantoin. In 2 cases, diphenylhydantoin could not be detected in the serum when combined with doses of phenobarbital above 1 mg. per kilogram per day. Other cases showed either a lowering of hydantoin levels or no change in the presence of phenobarbital. A method is presented which permits the quantitation of these two drugs and primidone from the same 0.5 ml. sample of serum. Serum half‐life of phenobarbital in 6 children was in the range of 37 to 73 hours. This is a lower range than that published for adults