Comparisons of persistence and durability among three oral antidiabetic therapies using electronic prescription-fill data: the impact of adherence requirements and stockpiling

Clin Pharmacol Ther. 2011 Dec;90(6):813-9. doi: 10.1038/clpt.2011.228. Epub 2011 Nov 2.


Two important challenges are inherent in the design of studies using prescription data from electronic health records: how to define the minimum level of adherence that would qualify as "continuous drug use" and how to handle stockpiling of medications. Generally, the sensitivity of a study's conclusions to these design choices is not analyzed. In our study, covariate adjusted Cox models were used to compare persistence and durability with respect to three common oral antidiabetic therapies in a cohort of 12,697 incident users. Assuming 50% stockpiling, sulfonylurea therapy, as compared with metformin, showed a significantly lower risk of nonpersistence (changing or stopping therapy) when no gap days were allowed (HR 0.95, P = 0.032), no significant difference when 14 gap days were allowed (HR 0.99, P = 0.536), and significantly greater risk of nonpersistence when 30 gap days were allowed (HR 1.05, P = 0.046). All the drug comparisons showed statistically significant effects in both directions, the risk of nonpersistence increasing or decreasing depending on the design parameters.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Administration, Oral
  • Aged
  • Cohort Studies
  • Electronic Health Records / statistics & numerical data*
  • Female
  • Follow-Up Studies
  • Humans
  • Hypoglycemic Agents / administration & dosage
  • Hypoglycemic Agents / supply & distribution
  • Hypoglycemic Agents / therapeutic use*
  • Male
  • Medication Adherence / statistics & numerical data*
  • Metformin / administration & dosage
  • Metformin / supply & distribution
  • Metformin / therapeutic use
  • Middle Aged
  • Proportional Hazards Models
  • Research Design*
  • Retrospective Studies
  • Sulfonylurea Compounds / administration & dosage
  • Sulfonylurea Compounds / supply & distribution
  • Sulfonylurea Compounds / therapeutic use


  • Hypoglycemic Agents
  • Sulfonylurea Compounds
  • Metformin