[Generic substitution in primary care in 2011: differences according to pharmacological classes?]

Abstract

Background: Generic substitution has been permitted for several years in France and is promoted in order to reduce health expenditures. However, reluctance concerning use of generic drugs exists for different reasons: suspicions about their efficacy and/or safety, differences in content (excipients) and discussions about bioequivalency. The aim of our study was to determine whether or not the substitution ratio differs according to pharmacological classes used in primary care.

Methods: We conducted a descriptive study in the French Health Insurance Database using reimbursement data on drugs prescribed and delivered in the Midi-Pyrénées administrative district between March 2010 and March 2011. We selected different pharmacological classes largely used in primary care. For each class, a substitution ratio was calculated (DDD of generics delivered/DDD of brand name plus generics). A Chi(2) test was used in order to detect a difference between these substitution ratios.

Results: The global substitution ratio was 72.32%. Values varied from 28.36% for thyroid hormones to 90.39% for antibiotics, with significant statistical difference (P<0.001). The substitution ratio was less than 50% for thyroid hormones (28.36%) and antiepileptics (45.28%). Higher substitution ratios were observed for protein pump inhibitors (88.81%), statins (87.81%), antidepressors (87.37%) and diuretics (86.1%).

Conclusion: This study highlights major differences in terms of the generic substitution ratio between different pharmacological classes. This difference can be explained in part by published guidelines. Further studies are needed to ascertain the precise point of view of patients, general practitioners and pharmacists concerning this issue.

Keywords: Generic drugs; Generic substitution; Médicaments génériques; Primary care; Soins primaires; Substitution.