Developing Canadian Defined Daily Doses for Animals: A Metric to Quantify Antimicrobial Use

Area of Science:

• Veterinary pharmacology
• Antimicrobial stewardship
• Drug utilization research

Background:

• Standardized analysis of antimicrobial use data is crucial for effective surveillance and policy development in veterinary medicine.
• Defined daily doses for animals (DDDvet) provide a harmonized metric for quantifying antimicrobial consumption in livestock.
• Existing DDDvet principles from the European Medicines Agency (EMA) require adaptation for Canadian veterinary practices.

Purpose of the Study:

• To develop and describe the methodology for assigning Canadian veterinary defined daily doses (DDDvetCAs) for pigs and poultry.
• To establish DDDvetCA standards for authorized and compounded antimicrobial active ingredients used in Canada, including extra-label uses.
• To compare the newly developed DDDvetCAs with existing EMA DDDvet values where applicable.

Main Methods:

• Species-specific DDDvetCAs were calculated based on the average of unique daily doses from product information.
• Data were stratified by route of administration (feed, water, bolus, injectable) and age indication.
• Comparisons were made between Canadian DDDvetCAs and EMA DDDvets for matched antimicrobial active ingredients and administration routes.

Main Results:

• Seventy-five DDDvetCAs were assigned for pigs and 51 for poultry.
• Seventeen injectable DDDvetCAs were compared to 14 EMA parenteral DDDvets, and 53 oral/feed/water/bolus DDDvetCAs to 40 EMA oral DDDvets.
• Feed and water DDDvetCAs were generally lower than EMA oral DDDvets, with methodological differences complicating direct comparisons.

Conclusions:

• The development of DDDvetCAs provides essential metrics for monitoring antimicrobial exposure in Canadian livestock.
• These standards will support risk assessment, inform stewardship policies, and facilitate national surveillance of antimicrobial use and resistance.
• Adopting harmonized DDD standards is vital for international comparisons, though differences in licensed antimicrobials present challenges.