Anatomical Therapeutic Chemical Classification System
Overview
The Anatomical Therapeutic Chemical (ATC) Classification System is a drug classification system that categorizes active ingredients of drugs according to the organ or system on which they act and their therapeutic, pharmacological, and chemical properties. It is controlled by the World Health Organization Collaborating Centre for Drug Statistics Methodology (WHOCC), and it is used for drug utilization research to improve quality of drug use.
History
The ATC classification system was first published by the WHOCC in 1976. The aim was to introduce a universal standard for classifying drugs to serve the needs of drug utilization research, thus providing a useful tool for improving the quality of drug use. Over the years, the system has been revised and updated to reflect changes in the pharmaceutical industry and the evolution of medical knowledge.
Structure
The ATC classification system has a hierarchical structure with five different levels. The drugs are divided into fourteen main groups (1st level), with pharmacological/therapeutic subgroups (2nd level). The 3rd and 4th levels are chemical/pharmacological/therapeutic subgroups, and the 5th level is the chemical substance. The 2nd, 3rd, and 4th levels are often used to identify pharmacological subgroups when that is considered more appropriate.
Classification Process
The classification of a substance into the ATC system is based on the main therapeutic use of the main ingredient according to the indication in the country of marketing. The classification process is guided by a set of rules and guidelines established by the WHOCC. The process involves several steps, including the evaluation of the new substance, the assignment of a temporary ATC code, and the final assignment of a permanent ATC code.
Applications
The ATC classification system is used worldwide for a variety of applications. It is used in drug utilization research to monitor and compare drug usage across different countries and to monitor the effect of policy changes on drug use. It is also used in clinical research to compare the effects of different drugs and drug classes on disease outcomes. Moreover, it is used in pharmacovigilance to identify drug safety issues related to specific drugs or drug classes.
Limitations
Despite its wide usage, the ATC classification system has some limitations. It does not cover all medicines, and some drugs may be difficult to classify due to their complex nature. In addition, the system may not reflect the current use of a drug, as it is based on the indication at the time of marketing. Furthermore, the system does not account for off-label use of drugs, which can be a significant factor in drug utilization.
Future Developments
The WHOCC continues to update and refine the ATC classification system to ensure its relevance and utility. Future developments may include the addition of new drug classes, the refinement of existing classifications, and the development of new methodologies for drug classification.