Generic - equivalent drugs use in internal and general medicine patients: distrust, confusion, lack of certainties or knowledge? Part 1. Pharmacological issues

Despite compelling evidence and guidelines, in Italy, generic/equivalent drugs are still underused. The failure to adopt existing generic drugs may result into a missed opportunity to further reduce healthcare costs. Equivalent drugs are approved based on data deriving from bioequivalence studies. In the first part of the article, the concepts of generic/equivalent drugs are defined, emphasizing the differences between pharmaceutical equivalence, therapeutic equivalence, bioequivalence and bioavailability. A summary of the methods adopted to define bioequivalence (pharmacokinetic studies; pharmacodynamic studies; comparative clinical trials; in vitro studies) is also included.