Pharmaceutical expert information is characterized by steady increase in extent and complexity as well as by strong interweavement and penetration with interdependent references. These properties suggest the utilization of modern hypermedia technology, organizing knowledge as a network of linked pieces, enabling more intuitive, faster and easier navigation within the growing information space. There is a need for a suitable, role oriented external representation of pharmaceutical expert information. The application of pharmaceutical expert information when analyzing medications for contraindications and interactions is mainly mechanical in nature. It requires to follow references and to compare codes. The electronic availability of medication information, which is often forced by drug dispensing systems, is not exhausted when these procedures are performed manually at the screen. There is a need for automatization of these procedures. This automatization requires a suitable internal representation of pharmaceutical expert information. The universality of pharmaceutical information systems leaves open their conceptual environment. The different kinds of application scenarios pose strong requirements on the formalization of expert information. A universal representation has to be found which captures the nature of pharmaceuticals including common properties of drug classification systems. The diversity of the latters within the different healthcare organisations is to be regarded as the most serious barrier aggravating global communication within the healthcare system.