title: Projected economic impact of clinical findings of generic entry of topiramate on G4 European countries.
abstract: OBJECTIVE
  To explore the effects of generic substitution of the antiepileptic drug (AED) topiramate (Topamax) in Canada; to convert observed Canadian costs into the settings of France, Germany, Italy, and the United Kingdom (UK); and to forecast the economic impact of generic topiramate entry in these four European countries.
  
  
  METHODS
  Health claims from Régie de l'assurance maladie du Québec (RAMQ) plan (1/2006-9/2008) and IMS Health data (1998-2008) were used. Patients with epilepsy and > or = 2 topiramate dispensings were selected. An open-cohort design was used to classify observation into mutually-exclusive periods of branded versus generic use of topiramate. Canadian healthcare utilization and costs (2007 CAN$/person-year) were compared between periods using multivariate models. Annualized per-patient costs (2007 euro or 2007 pound sterling/person-year) were converted using Canadian utilization rates, European prices and service-use ratios. Non-parametric bootstrap served to assess statistical significance of cost differences. Topiramate market was forecasted following generic entry (09/2009-09/2010) using autoregressive models based on the European experience. The economic impact of generic topiramate entry was estimated for each country.
  
  
  RESULTS
  A total of 1164 patients (mean age: 39.8 years, 61.7% female) were observed for 2.6 years on average. After covariates adjustment, generic-use periods were associated with increased pharmacy dispensings (other AEDs: +0.95/person-year, non-AEDs: +12.28/person-year, p < 0.001), hospitalizations ( + 0.08/person-year, p = 0.015), and lengths of hospital stays (+0.51 days/person-year, p < 0.001). Adjusted costs, excluding topiramate, were CAN$1060/person-year higher during generic use (p = 0.005). Converted per-patient costs excluding topiramate were significantly higher for generic relative to brand periods in all European countries (adjusted cost differences per person-year: 706-815 euro, p < 0.001 for all comparisons). System-wide costs would increase from 3.5 to 24.4% one year after generic entry.
  
  
  CONCLUSIONS
  Study limitations include the absence of indirect costs, possible claim inaccuracies, and IMS data limitations.
  
  
  CONCLUSIONS
  Higher health costs were projected for G4 European countries from the Canadian experience following the generic entry of topiramate.
authors.affiliation: Groupe d'analyse, Ltée, Montréal, Québec, Canada.
authors.forename: Pierre Emmanuel
authors.initials: PE
authors.lastname: Paradis
authors.forename: Dominick
authors.initials: D
authors.lastname: Latrémouille-Viau
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Moore
authors.forename: Natalia
authors.initials: N
authors.lastname: Mishagina
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Lafeuille
authors.forename: Patrick
authors.initials: P
authors.lastname: Lefebvre
authors.forename: Maren
authors.initials: M
authors.lastname: Gaudig
authors.forename: Mei Sheng
authors.initials: MS
authors.lastname: Duh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000191:economics / Q000627:therapeutic use; D002170:Canada; D002648:Child; D002675:Child, Preschool; D016568:Drugs, Generic / Q000191:economics* / Q000627:therapeutic use*; D005060:Europe; D005062:European Union / Q000191:economics*; D005260:Female; D005544:Forecasting; D005632:Fructose / Q000031:analogs & derivatives* / Q000191:economics / Q000627:therapeutic use; D017048:Health Care Costs; D006295:Health Resources / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D000077236:Topiramate; D055815:Young Adult
chemical_list: D000927:Anticonvulsants; D016568:Drugs, Generic; D000077236:Topiramate; D005632:Fructose