title: Time Series Analysis on the Impact of Generic Substitution and Reference Pricing on Antipsychotic Costs in Finland.
abstract: OBJECTIVE
  To analyze the medium- to long-term impact of generic substitution and the reference price system on the daily cost of antipsychotics in Finland. The additional impact of reference pricing over and above previously implemented generic substitution was also assessed.
  
  
  METHODS
  An interrupted time series design with a control group and segmented regression analysis was used to estimate the effect of the implementation of generic substitution and the reference price system on the daily cost of antipsychotics. The data have 69 monthly values of the average daily cost for each of the studied antipsychotics: 39 months before and 30 months after the introduction of reference pricing. For one of the studied antipsychotic, the time before the introduction of reference pricing could be further divided into time before and after the introduction of generic substitution.
  
  
  RESULTS
  According to the model, 2.5 years after the implementation of reference pricing, the daily cost of the studied antipsychotics was 24.6% to 50.6% lower than it would have been if reference pricing had not been implemented. Two and a half years after the implementation of the reference price system, however, the additional impact of reference pricing over and above previously implemented generic substitution was modest, less than 1 percentage point.
  
  
  CONCLUSIONS
  Although the price competition induced by reference pricing decreased the prices of antipsychotics in Finland in the short-term, the prices had a tendency to stagnate or even to turn in an upward direction in the medium- to long-term. Furthermore, the additional impact of reference pricing over and above previously implemented generic substitution remained quite modest.
authors.affiliation: The Social Insurance Institution, Research Department, Helsinki, Finland. Electronic address: hanna.koskinen@kela.fi.
authors.forename: Hanna
authors.initials: H
authors.lastname: Koskinen
authors.affiliation: The Social Insurance Institution, Research Department, Helsinki, Finland.
authors.forename: Hennamari
authors.initials: H
authors.lastname: Mikkola
authors.affiliation: The Social Insurance Institution, Research Department, Helsinki, Finland.
authors.forename: Leena K
authors.initials: LK
authors.lastname: Saastamoinen
authors.affiliation: The Social Insurance Institution, Research Department, Helsinki, Finland.
authors.forename: Elina
authors.initials: E
authors.lastname: Ahola
authors.affiliation: The Social Insurance Institution, Research Department, Helsinki, Finland.
authors.forename: Jaana E
authors.initials: JE
authors.lastname: Martikainen
mesh_terms: D014150:Antipsychotic Agents / Q000191:economics*; D003363:Cost Control; D003365:Costs and Cost Analysis / Q000191:economics* / Q000379:methods*; D057915:Drug Substitution / Q000191:economics*; D005387:Finland; D006801:Humans; D012044:Regression Analysis
chemical_list: D014150:Antipsychotic Agents
keywords: cost-containment policy; generic substitution; reference pricing; segmented linear regression analysis