A critical look at phenytoin use for early post-traumatic seizure prophylaxis.

Background: The American Academy of Neurology recommended using phenytoin or carbamazepine to prevent early post-traumatic seizures (PTS) in severe traumatic brain injuries (TBI). In this study, we examined the effects of using phenytoin prophylaxis on mild, moderate, and severe TBIs. There have been no studies looking at compliance rate and side effects of systematic use of phenytoin at a large population scale. The goal of this study is to determine 1) the proportion of TBI patients receiving phenytoin prophylaxis; 2) which parameters decided when to decide administer phenytoin; 3) prophylaxis efficacy and complication rate.

Methods: We retrospectively studied all patients admitted with a TBI over a two year-period and collected the following information: age, GCS score, CT-scan Marshall grade, incidence of early PTS, incidence of phenytoin use and time delay, side effects, and incidence of over-dosage or under-dosage.

Results: 1008 patients were included. 5.4 % had early PTS, 2.3 % while on prophylaxis and 3.1% while not on prophylaxis, 1.9% before reaching the hospital and 1.2% prior to phenytoin administration while in hospital. Delay of administration was 5 hours. 64.8% received prophylaxis and physicians used positive CT scan as the primary decision-making parameter (p<.001). Compliance with guidelines was 99.7%. Adverse reactions occurred in 0.5%. Levels were drawn in 42.2% (52% therapeutic, 41% low, 7% high).

Conclusions: Phenytoin is used according to guidelines, with CT scan being the main decision factor for its use. The frequency of early PTS rate is low and side effects are rare. However, earlier administration of phenytoin and adequate levels could further prevent early PTS.