Generic switching and non-persistence among medicine users: a combined population-based questionnaire and register study

PLoS One. 2015 Mar 16;10(3):e0119688. doi: 10.1371/journal.pone.0119688. eCollection 2015.

Abstract

Background: Generic substitution means that one medicinal product is replaced by another product containing the same active substance. It is strictly regulated with respect to its bioequivalence, and all products must have undergone appropriate studies. Although generic substitution is widely implemented, it still remains to be answered how generic switch influences persistence to long-term treatment, and if it is modified by patients' concerns about medicine and views on generic medicine. This study focuses on users of antidepressants and antiepileptics, and their experience of generic switching.

Methods: The study was an observational cohort study. By use of a prescription database, we identified patients who had redeemed prescriptions on generically substitutable drugs, and a questionnaire was mailed to them. We analyzed predictors of discontinuation in relation to generic switch and patients' attitudes towards generic medicines and concerns about their medicine.

Results: Patients who experience their first-time switch of a specific drug were at higher risk of non-persistence, Hazard Ratio 2.98, 95% CI (1.81;4.89) versus those who have never switched, and 35.7% became non-persistent during the first year of follow-up. Generic switching did not influence persistence considerably in those having previous experience with generic switching of the specific drug. Stratified analyses on users of antidepressants and antiepileptics underpin the results, showing higher risk of non-persistence for first-time switchers for both drug categories.

Conclusion: In conclusion, patients who are first-time switchers of a specific drug were at higher risk of non-persistence compared to never switchers and those having experienced previous generic switching.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Anticonvulsants / therapeutic use*
  • Antidepressive Agents / therapeutic use*
  • Denmark
  • Drug Substitution / statistics & numerical data
  • Drugs, Generic / therapeutic use*
  • Female
  • Health Surveys
  • Humans
  • Male
  • Middle Aged
  • Patient Compliance / statistics & numerical data
  • Registries
  • Therapeutic Equivalency
  • Young Adult

Substances

  • Anticonvulsants
  • Antidepressive Agents
  • Drugs, Generic

Grant support

The study was partly funded through a contract with the Danish Ministry of Health, tender number 2007/S145-180398, the Region of Southern Denmark Research PhD Foundation (j.nr: 11/28042) and the Region of Southern Denmark Research Foundation (j.nr: 12/21277). The funder (The Danish Ministry of Health) initiated this study, but the authors designed the study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.