Problems associated with the ATC system of drug classification

Area of Science:

• Pharmacology
• Drug Utilization Studies
• Health Informatics

Background:

• The Anatomical Therapeutic Chemical (ATC) classification system is the global standard for drug utilization research.
• Despite its widespread use, the ATC system exhibits structural and conceptual limitations.
• These limitations impact the accuracy and consistency of drug utilization data.

Purpose of the Study:

• To evaluate the consistency, completeness, and terminology of the ATC classification system.
• To identify systemic weaknesses and propose potential improvements or alternatives.
• To assess the ATC system's suitability for modern pharmacotherapy.

Main Methods:

• Systematic analysis of all 14 ATC main groups and sublevels using the "ATC/DDD Index 2025" and WHO "2025 guideline".
• Examination of classification logic, therapeutic area coverage, handling of combination products, and terminology.
• Documentation of discrepancies within and across ATC groups.

Main Results:

• Widespread inconsistencies were found in the ATC system's classification logic, mixing anatomical, therapeutic, pharmacological, chemical, and miscellaneous principles.
• Inadequate handling of combination products and drugs with multiple indications leads to fragmentation, overlaps, and duplications.
• Vague or outdated terminology obscures pharmacological mechanisms and reflects historical rather than scientific rationale.

Conclusions:

• The ATC classification system demonstrates systematic deficiencies that hinder accurate drug utilization analyses.
• Its current structure is ill-suited for contemporary drug development, multi-indicational drugs, and rational prescribing.
• A mechanistically oriented system based on pharmacological properties and molecular targets is recommended for a more consistent and adaptable framework.