COMPARATIVE BIOAVAILABILITY OF A GENERIC PHENYTOIN AND DILANTIN

Generic substitution of antiepileptic drugs (AEDs) has been controvers ial, with many alleged instances of biologic and therapeutic inequival ence reported. The recall of a generic phenytoin (PHT) formulation use d in the Veterans Administration (VA) medical system allowed us to eva luate the question of biologic equivalence systematically in a relativ ely large number of patients at the Bronx VA Medical Center. Serum PHT levels were 22-31% lower during the period of generic intake as compa red with levels in the same patients receiving Dilantin. Review of the literature showed only one other adequately documented report of pote ntial clinically significant inequivalence between a brand name and ge neric AED. Despite the apparent infrequency of generic inequivalence, several areas in which procedures for certification of therapeutic equ ivalence should be improved were identified.