Altered phenytoin clearance with febrile illness.

Abstract

A prospective study was performed of antiepileptic drug levels in 14 boys resident in a pediatric chronic care facility. Blood samples and 24-hour urine collections were obtained monthly. During febrile illness (temperature greater than 101 degrees F for more than 24 hours), six additional blood samples and two urine collections were obtained for each child. During 8 of 10 febrile illnesses, phenytoin (PHT) decreased more than 40% from pre-illness baseline. Mean PHT level before illness was 16.7 (+/- 4.5 micrograms/ml) and during illness, 8.2 (+/- 3.6 micrograms/ml), significantly lower (p less than 0.001). Neither PHT binding nor absorption was altered by illness, so the most probable cause of the drop in PHT levels was induction of the hepatic oxidative enzyme system.