title: The effect of access restrictions on the vintage of drugs used by Medicaid enrollees.
abstract: OBJECTIVE
  To examine the extent to which recent Medicaid drug access restrictions, such as preferred drug lists (PDLs), may affect the vintage (or time since Food and Drug Administration approval) of 6 types of drugs used by Medicaid beneficiaries.
  
  
  METHODS
  Retrospective claims database analysis using National Drug Code pharmacy claims data.
  
  
  METHODS
  A regression model was developed to analyze the effect that Medicaid access restrictions had on the vintage of medications prescribed in 6 different therapeutic categories. A "difference in differences" approach was used to compare the change in vintage of medications prescribed in Medicaid versus non-Medicaid patients between the January-June 2001 and July-December 2003 study periods.
  
  
  RESULTS
  The results of the regression model showed that PDLs increased the age of Medicaid prescriptions by less than 1 year for drugs in 5 of the 6 therapeutic classes analyzed. In the case of pain management medications, the increase was more than 1.2 years.
  
  
  CONCLUSIONS
  The results of the regression model suggest that Medicaid drug access restriction programs (e.g., PDLs) have resulted in an increase in the age of drugs prescribed for Medicaid beneficiaries versus non-Medicaid patients. Since previous research has suggested a clinical and economic advantage to utilizing newer versus older drugs, further research should be conducted to explore how these medication restriction policies may unduly affect Medicaid beneficiaries compared with privately insured patients.
authors.affiliation: Graduate School of Business, Columbia University, New York, NY 10027, USA. frank.lichtenberg@columbia.edu
authors.forename: Frank R
authors.initials: FR
authors.lastname: Lichtenberg
mesh_terms: D011307:Drug Prescriptions / Q000145:classification*; D004363:Drug Utilization / Q000191:economics / Q000639:trends*; D018954:Drugs, Essential / Q000191:economics / Q000600:supply & distribution*; D005569:Formularies as Topic; D020793:Gatekeeping; D006297:Health Services Accessibility / Q000191:economics / Q000639:trends*; D006801:Humans; D007345:Insurance Claim Review; D008484:Medicaid / Q000331:legislation & jurisprudence*; D012189:Retrospective Studies; D014481:United States
chemical_list: D018954:Drugs, Essential