title: Induction of hypersensitivity to a previously tolerated antiepileptic drug by a second antiepileptic drug.
abstract: OBJECTIVE
  To describe the induction of hypersensitivity to one antiepileptic drug (AED) by a second AED.
  
  
  METHODS
  Case report and review of the relevant literature.
  
  
  RESULTS
  A patient is reported who was treated with phenytoin (PHT) for 6 months without adverse effect, but developed a hypersensitivity reaction with rash, fever, elevated liver enzymes, lymphadenopathy, and colitis 6 weeks after the introduction of carbamazepine (CBZ). PHT and CBZ were discontinued. Seizures continued despite treatment with valproic acid and clobazam. A decision was made to cautiously reintroduce PHT. Diffuse skin rash and pharyngitis appeared after two doses of PHT.
  
  
  CONCLUSIONS
  The AED hypersensitivity syndrome has been thought to occur as a consequence of preexisting pharmacogenetic and immunologic abnormalities. Our case demonstrates induction of hypersensitivity to an AED that had been formerly well tolerated, after a hypersensitivity reaction to another AED. This is distinct from simple cross-reactivity between one or more drugs. Such induction of hypersensitivity with AEDs has not been previously described.
authors.affiliation: Division of Neurology, Dalhousie University, Halifax, Nova Scotia, Canada.
authors.forename: B D
authors.initials: BD
authors.lastname: Klassen
authors.forename: R M
authors.initials: RM
authors.lastname: Sadler
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects* / Q000276:immunology*; D002220:Carbamazepine / Q000009:adverse effects* / Q000276:immunology*; D003429:Cross Reactions / Q000276:immunology; D003875:Drug Eruptions / Q000209:etiology / Q000276:immunology; D004342:Drug Hypersensitivity / Q000209:etiology* / Q000276:immunology*; D004359:Drug Therapy, Combination; D004827:Epilepsy / Q000188:drug therapy* / Q000276:immunology; D006801:Humans; D008297:Male; D010597:Pharmacogenetics; D010672:Phenytoin / Q000009:adverse effects* / Q000276:immunology*
chemical_list: D000927:Anticonvulsants; D002220:Carbamazepine; D010672:Phenytoin