2. Some regulatory aspects of the pharmaceutical sector

The need to study the polymorphism and physical properties of active ingredients and excipients has long been recognized by the health authorities issuing marketing authorizations. However, the "guidelines" were not at all detailed as to how to set up a study strategy and define quality standards for both the active ingredient and the finished product. To the best of our knowledge, one of the first articles on this subject was by Byrn et al. [53] , who presented 4 decision trees dealing with the studies to be carried out in the case of polymorphism, hydrates/solvates, desolvated solvates and amorphous phases. On the basis of this initial work, the ICH (International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use) published a Q6A guideline [54]...