ATC code N Nervous system is a section of the Anatomical Therapeutic Chemical Classification System, a system of alphanumeric codes developed by the WHO for the classification of drugs and other medical products.

Codes for veterinary use (ATCvet codes) can be created by placing the letter Q in front of the human ATC code: QN... ATCvet codes without corresponding human ATC codes are cited with the leading Q in the following list.

National issues of the ATC classification may include additional codes not present in this list, which follows the WHO version.

The Anatomical Therapeutic Chemical (ATC) Classification System is used for the classification of drugs. It is controlled by the WHO Collaborating Centre for Drug Statistics Methodology (WHOCC), and was first published in 1976.

This pharmaceutical coding system divides drugs into different groups according to the organ or system on which they act and/or their therapeutic and chemical characteristics. Each bottom-level ATC code stands for a pharmaceutically used substance in a single indication (or use). This means that one drug can have more than one code: acetylsalicylic acid (aspirin), for example, has A01AD05 as a drug for local oral treatment, B01AC06 as a platelet inhibitor, and N02BA01 as an analgesic and antipyretic. On the other hand, several different brands share the same code if they have the same active substance and indications.

In this system, drugs are classified into groups at 5 different levels:

The first level of the code indicates the anatomical main group and consists of one letter. There are 14 main groups:

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