Insights into the definition of terms in European medical device regulation.

INTRODUCTION: Medical devices comprise apparatus/instruments, software, and materials with therapeutic activities obtained by principal mechanisms of action different from pharmacological, immunological and metabolic, which are proper of medicinal products. In this context the key for the distinction between medicinal products and devices lies in the correct interpretation of these terms, which, although defined in a guideline, are still not univocally interpreted. Areas covered: This article discusses the definitions of pharmacological and non-pharmacological mechanisms of action, such as the chemical and physical means. The aim is to give insights on the correct definition these terms in order to contribute to build the desired synergy between scientific and regulatory fields and promote a correct interpretation of the European regulatory framework as well as sustainable health and innovation. Expert commentary: We propose a series of definitions and a method to interpret those definitions within possible decision tree paradigm. Specifically, we propose to define the difference between the terms 'action' of a medical device compared to the 'mechanism of action' of such device. In any decisional procedure the correct interpretation of these and other correlated terms is needed to correctly assess whether a substance is a medicinal product or a medical device.