1 Research Unit of General Practice, Department of Public Health, Det Sundhedsvidenskabelige Fakultet, SDU2 Research Unit of General Practice, Department of Public Health, Det Sundhedsvidenskabelige Fakultet, SDU
Associations between generic substitution and patient-related factors Jette Østergaard Rathe1, Pia V. Larsen1, Morten Andersen2, Janus L. Thomsen3, Maja S. Paulsen1, Jens Søndergaard1 1. Research Unit of General Practice, Institute of Public Health, University of Southern Denmark 2. Centre for Pharmacoepidemiology, Karolinska Institutet, Department of Medicine Solna, Stockholm, Sweden 3. Danish Quality Unit of General Practice, Odense, Denmark Background Generic substitution means that chemically equivalent but less expensive drugs are dispensed in place of a brand name product. Although generic medicines by definition are bioequivalent to their brand name counterparts there are concerns about whether generic substitution is always accompanied by clinical equivalence in terms of effectiveness and that it may cause concerns and thereby causing some skepticism towards generic substitution. There is, however, a lack of knowledge about whether some groups of patients may be influenced by drug-switching. Research questions We want to identify the characteristics that distinguish the two patient groups: One group that has experienced a generic switch and one that has not. Methods A cross-sectional questionnaire was made on beliefs about medicine, views on generic medicine and confidence in the health care system. The study comprised 2476 patients (736 users of antidepressants, 795 users of antiepileptics and 945 users of other substitutable drugs). For each patient we focused on one purchase of a generically substitutable drug. Data were linked with a prescription database. Results We found no associations between generic substitution and, respectively, gender, age, drug group and polypharmacy. Earlier switches of the index drug are statistically significant associated with acceptance of generic substitution (adjusted OR 6.01 95% CI 4.77; 7.58). However, having switched more than 5 times with other prescribed medicine reduces the odds of receiving a generic switch of the index medicine (adjusted OR 0.70 95% CI 0.50;0.97). Negative views on generic medicines had a significant negative effect on switching generics in the antiepileptic and antidepressant groups (antiepileptics OR 0.37 and antidepressants OR 0.53). Conclusion We did not find any patient-related factors associated with generic substitution; however, patients who have once experienced a generic substitution with a specific drug are more likely to switch again despite skepticism towards generic substitution. Points for discussion at EGPRN Discussion of the results,-that no difference in gender, age, drug group or polypharmacy exists, irrespective of switching generics or not. Discussion of the reason why one earlier index ATC-code drug switching is positively associated with generic substitution, while ≥ 5 earlier switches with other ATC-code drug is negatively associated.