ATC Codes

ATC Codes Explained

The HPRA has recently commenced publishing ATC codes on the ‘Find a medicine’ webpage for each medicine.   This information may be useful when searching for individual medicines or classes of medicines.  

The Anatomical Therapeutic Chemical (ATC) Classification is an internationally accepted classification system for medicines that is maintained by the World Health Organisation (WHO). The WHO assigns ATC codes to all active substances contained in medicines based on the therapeutic indication for the medicine. Using the ATC code, active substances are classified in groups at five different levels according to the organ or system on which they act and their therapeutic, pharmacological and chemical properties.  Where the relevant information is available, a full ATC code will have 7 elements made up of letters and numbers.  In some cases, an ATC code is partially assigned with a reduced number of elements, and in other cases an ATC code is not assigned. 

Here is an example of how an ATC code is applied for a medicine containing the active substance omeprazole for the treatment of acid reflux and ulcers in the gut: 



ATC Code

  1. Main Group

Alimentary tract and metabolism


  1. Therapeutic Group

Drugs for acid-related disorders


  1. Pharmacological subgroup

Drugs for peptic ulcer and gastro-oesophageal reflux disease


  1. Chemical subgroup

Proton pump inhibitors


  1. Active substance



All medicines containing omeprazole as a single active substance are given the ATC code A02BC01.  Medicines containing omeprazole and one or more active substances are given a separate but related ATC code.

Further information on ATC codes is available from the WHO website.