Section 1 | Resistance, Stewardship, & Categories of Antimicrobials

Regulations on
Use and Access
Page 06 /

Categorization of Antimicrobial Drugs


Governments around the world have recognized the growing threat that antimicrobial resistance (AMR) has on the ability to treat life-threatening infections in humans.

Many of the same classes of antimicrobials used to treat and prevent infections in human medicine are also used in animals.

While the efficacy of drugs is important, there are some antimicrobials deemed more critical than others, based on being preferred options for treatment of serious infections in humans, and the availability or lack of alternative treatment options.

Criteria for Categorization

Health Canada is responsible for the microbiological safety assessment of veterinary antimicrobials pre- and post-market. When assigning categories to antimicrobial drugs, Health Canada considers the following:

  1. Indication – the severity of the bacterial infection, as well as the spectrum of activity of the drug
  2. Availability of alternative antimicrobial drugs – where limited alternatives are available, the drug is deemed more critical than an antimicrobial with alternative treatment options


As of December 1st, 2018 all medically important antimicrobials will be labeled with ‘responsible use’ statements. Look out for this symbol on all veterinary drugs containing medically important antimicrobials and be sure to use responsibly!


Table 1. Health Canada Categories for Antimicrobials

Category Description
I – Very High Importance These antimicrobials are essential for the treatment of serious human illnesses. Very few or no alternatives are available if these don’t work
II – High Importance These antimicrobials treat a variety of serious infections. Alternatives are generally available if needed, including Category I antimicrobials
III – Medium Importance These antimicrobials treat a variety of less serious infections. Alternatives are generally available, including Category I and II antimicrobials
IV – Low Importance Antimicrobials in this category are currently not used in human medicine


Table 2. Health Canada Classification of Antimicrobial Agents Based on Level of Importance in Human Medicine