Purpose: In aut-idem or generic substitution, discrepancies between summaries of product characteristics (SmPCs) referring to the same active substance (AS) may cause difficulties regarding informed consent and medical liability. The qualitative and quantitative characteristics of such discrepancies are insufficiently studied, impeding harmonization of same-substance SmPCs and compromising safe drug treatment.
Methods: SmPCs of the one hundred most frequently prescribed ASs in Germany were analyzed for discrepancies in the presentation of indications (Inds) and contraindications (CInds). Inclusion and exclusion criteria of drugs/SmPCs were chosen according to the standards of the aut-idem substitution in Germany.
Results: According to the study protocol, we identified 1486 drugs, of which 1426 SmPCs could be obtained. 41% respectively 65% of the ASs had same-substance SmPCs that differed from the respective reference SmPC in the number of listed Inds respectively CInds. The number of listed Inds/CInds varied considerably between same-substance SmPCs with maximum ranges in Inds of 7 in amoxicillin, and in CInds of 11 in lisinopril. Many ASs had large proportions (> 50%) of associated same-substance SmPCs that differed from the respective reference SmPC. A considerable proportion of ASs had same-substance SmPCs with formal and content-related differences other than the discrepancy in the number of Inds/CInds.
Conclusion: This evaluation of same-substance SmPCs shows a clear lack of harmonization of same-substance SmPCs. Considering that generic substitution has become the rule and that physicians usually do not know which drug the patient receives in the pharmacy, these discrepancies raise several questions, that require a separate legal evaluation.
Keywords: Aut-idem; Generic drug; Generic substitution; Package insert; Pharmacovigilance; Prescribing information.
© 2021. The Author(s).