title: Clinical and pharmacy utilization outcomes with brand to generic antiepileptic switches in patients with epilepsy.
abstract: OBJECTIVE
  To determine if switching from select branded to generic equivalent antiepileptic drugs (AEDs) in patients with epilepsy is associated with adverse outcomes.
  
  
  METHODS
  A retrospective cohort study using a large health insurance plan claims database comparing patients with epilepsy who switched from brand to generic equivalent phenytoin, lamotrigine, or divalproex after 6 months (switch cohorts) to matched patients who remained on the brand (nonswitch cohorts). Primary outcomes measured include the incidence rate ratio (IRR) of discontinuation of the index AED; change in dose of index AED or addition of another AED; and the event rate ratio (ERR) of the composite of all-cause emergency department (ED) visits or hospitalizations.
  
  
  RESULTS
  Lamotrigine and divalproex showed no differences in AED utilization changes between the switchers and nonswitchers [IRR for lamotrigine 1.00, 95% confidence interval (CI) 0.84-1.19; IRR for divalproex 1.02, 95% CI, 0.88-1.42]. Compared with nonswitchers, the phenytoin switch cohort had greater incidence of AED utilization changes (IRR 1.85, 95% CI 1.50-2.29). The switch versus nonswitch cohorts did not demonstrate differences in ED visits or hospitalizations for the studied AEDs (ERR for phenytoin 0.96, 95% CI 0.80-1.16; ERR for lamotrigine 0.97, 95% CI 0.80-1.17; ERR for divalproex 0.83, 95% CI 0.66-1.06).
  
  
  CONCLUSIONS
  Brand to generic switching of phenytoin was not associated with more clinical events but was associated with increased index drug discontinuations, dose changes, or therapy augmentations. Lamotrigine or divalproex brand to generic switching was not associated with increased incidence of events or utilization changes compared with patients remaining on the branded product. Changes in AED utilization may be more sensitive than ED visits and hospitalizations for detecting adverse outcomes.
authors.affiliation: Clinical Analytics andOutcomes Research, Prescription Solutions, 2300 Main Street, Irvine, CA 92614, U.S.A. sara_c_erickson@prescriptionsolutions.com
authors.forename: Sara C
authors.initials: SC
authors.lastname: Erickson
authors.forename: Lisa
authors.initials: L
authors.lastname: Le
authors.forename: Scott D
authors.initials: SD
authors.lastname: Ramsey
authors.forename: Brian K
authors.initials: BK
authors.lastname: Solow
authors.forename: Armen
authors.initials: A
authors.lastname: Zakharyan
authors.forename: Karen M
authors.initials: KM
authors.lastname: Stockl
authors.forename: Ann S M
authors.initials: AS
authors.lastname: Harada
authors.forename: Bradford
authors.initials: B
authors.lastname: Curtis
mesh_terms: D000927:Anticonvulsants / Q000009:adverse effects / Q000627:therapeutic use*; D057915:Drug Substitution / Q000009:adverse effects / Q000706:statistics & numerical data; D016568:Drugs, Generic / Q000009:adverse effects / Q000627:therapeutic use; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D000077213:Lamotrigine; D008297:Male; D008875:Middle Aged; D010672:Phenytoin / Q000009:adverse effects / Q000627:therapeutic use; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012189:Retrospective Studies; D016896:Treatment Outcome; D014227:Triazines / Q000009:adverse effects / Q000627:therapeutic use; D014635:Valproic Acid / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000927:Anticonvulsants; D016568:Drugs, Generic; D014227:Triazines; D014635:Valproic Acid; D010672:Phenytoin; D000077213:Lamotrigine