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.