MedDRA and IME lists

The Medical Dictionary for Regulatory Activities – MedDRA is a clinically validated medical terminology dictionary used by regulatory authorities and the pharmaceutical industry. It was developed due to the need for standardization of terminology between regulatory authorities and multinational pharmaceutical companies, as well as the need to minimize errors in the translation of terms, for electronic data transfer.

MSSO (Maintenance and Support Services Organization) is an organization that provides support to MedDRA, which includes maintenance, distribution, implementation and development of MedDRA in accordance with the needs of users. The MedDRA structure is organized in hierarchical levels of which the highest level is System Organ Class (SOC), followed by High Level Group Term (HLGT), High Level Term (HLT), Preferred Term (PT) and Lowest Level Term (LLT). A characteristic of MedDRA is multiaxiality which is characterized by the concept of multiple organ systems. Namely, one PT can be connected to one or more organ systems. MedDRA may manifest multiaxiality on PT, HLT or HLGT levels.

According to the Rulebook on the method of reporting, collecting and monitoring adverse reactions to medicines (“Official Gazette of RS,” No. 64/2011), the marketing authorization holder or the person responsible for pharmacovigilance shall code all ICSR adverse reactions by using the MedDRA system.

The expert working group in the European Medicines Agency (EudraVigilance Expert Working Group) has initiated the development of the important medical event (IME) terms list in order to facilitate the classification, analysis and assessment of collected data by the marketing authorization holders/persons responsible for pharmacovigilance in day-to-day pharmacovigilance activities.

The IME list is based on PT level coding in MedDRA. This level is mostly used for database searches and data analysis. If an adverse reaction is encoded in LLT based on verbatim, parent categories shall be automatically added to it based on the hierarchical system, hence the severity of LLT should be checked by the associated PT.


Every adverse reaction on the PT level in the IME list has one designation: CS (core serious) or ES (extended serious).

Every adverse reaction on the IME list shall be considered  an important medical event and shall always be coded as serious.