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Updated: May 1, 2026

Evidence-based Knowledge Synthesis and Hypothesis Validation: Navigating Biomedical Knowledge Bases via Explainable AI and Agentic Systems
Published on: June 13, 2025
Formalizing MedDRA to support semantic reasoning on adverse drug reaction terms
Cédric Bousquet1, Éric Sadou2, Julien Souvignet1
1INSERM, U1142, LIMICS, F-75006, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, UMR_S 1142, LIMICS, F-75006, Paris, France; Université Paris 13, Sorbonne Paris Cité, LIMICS, (UMR_S 1142), F-93430, Villetaneuse, France; University of Saint Etienne, Department of Public Health and Medical Informatics, Saint-Etienne, France.
Abstract:
Although MedDRA has obvious advantages over previous terminologies for coding adverse drug reactions and discovering potential signals using data mining techniques, its terminological organization constrains users to search terms according to predefined categories. Adding formal definitions to MedDRA would allow retrieval of terms according to a case definition that may correspond to novel categories that are not currently available in the terminology. To achieve semantic reasoning with MedDRA, we have associated formal definitions to MedDRA terms in an OWL file named OntoADR that is the result of our first step for providing an "ontologized" version of MedDRA. MedDRA five-levels original hierarchy was converted into a subsumption tree and formal definitions of MedDRA terms were designed using several methods: mappings to SNOMED-CT, semi-automatic definition algorithms or a fully manual way. This article presents the main steps of OntoADR conception process, its structure and content, and discusses problems and limits raised by this attempt to "ontologize" MedDRA.
Insights
Formal definitions were added to the Medical Dictionary for Regulatory Activities (MedDRA) to enable semantic reasoning and overcome its hierarchical limitations. This "ontologized" MedDRA, called OntoADR, facilitates novel category discovery for adverse drug reaction data mining.
Area of Science:
- Pharmacovigilance and Drug Safety
- Medical Informatics and Ontologies
- Computational Linguistics and Terminology
Background:
- The Medical Dictionary for Regulatory Activities (MedDRA) is crucial for coding adverse drug reactions (ADRs) and signal detection.
- MedDRA's hierarchical structure limits flexible searching and the discovery of novel adverse event categories.
- Integrating formal definitions can enhance MedDRA's utility for semantic reasoning and data mining.
Purpose of the Study:
- To develop an "ontologized" version of MedDRA, named OntoADR, by associating formal definitions with its terms.
- To enable semantic reasoning and overcome the constraints of MedDRA's predefined categories.
- To facilitate the retrieval of terms based on case definitions, potentially revealing novel categories.
Main Methods:
- Converted MedDRA's five-level hierarchy into a subsumption tree.
- Developed formal definitions for MedDRA terms using multiple approaches: mapping to SNOMED-CT, semi-automatic algorithms, and manual curation.
- Created an OWL (Web Ontology Language) file, OntoADR, to store the formalized MedDRA terms and definitions.
Main Results:
- Successfully created OntoADR, an "ontologized" version of MedDRA with associated formal definitions.
- Demonstrated a method for enhancing MedDRA's terminological organization through formal semantics.
- Identified challenges and limitations inherent in the process of ontologizing MedDRA.
Conclusions:
- The OntoADR project represents a significant step towards enabling semantic reasoning with MedDRA.
- Formal definitions enhance MedDRA's capability for data mining and adverse drug reaction signal discovery beyond its inherent structure.
- Further development is needed to address the identified problems and limitations in creating a comprehensive ontologized MedDRA.
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