Food and Drug Administration officials plan to provide more context in reports on antimicrobials administered to livestock by estimating the quantities of drugs administered to individual species on a milligrams per kilogram of body weight basis.
The agency publishes annual data on the amounts, by total weights, of antimicrobial drugs sold for use in cattle, chickens, pigs, and turkeys, and reports issued so far have covered years 2009-15. The data in those reports have been totals for all species, rather than separated by species, but the agency began requiring this year that drug companies provide species-specific estimates of antimicrobial ingredient sales.
Agency officials announced in August plans to further increase the detail provided by developing biomass denominators, or estimates of the total weights of each species, using population estimates and the mean weight of animals of each species.
Those denominators would be used with drug sales data to give insights into shifts in sales and the causes for changes, supporting agency efforts to encourage judicious use in food-producing animals, FDA information states. Agency officials plan to calculate milligram per kilogram values for at least the antimicrobial drug classes that are shared with human medicine.
A European Union program uses similar measurements in analyzing antimicrobial sales data, Canada's government is developing a biomass denominator, and the World Organisation for Animal Health (OIE) is considering use of a biomass denominator as the organization develops a database on amounts of antimicrobials sold for administration to food-producing animals, FDA information states.
Past FDA antimicrobial sales reports have indicated most antimicrobials administered to livestock were sold over the counter and considered to be medically important because they are used in human medicine. The FDA's report for 2015, the most recent available, indicates such drugs accounted for about 21 million pounds of the 34 million sold that year.
When counting only the drugs considered important for human medicine, at least 97 percent were distributed in 2015 for over-the- counter availability, and 95 percent were sold for administration through feed or water.
The rules governing use of many antimicrobials on farms changed Jan. 1, when requirements for veterinarian oversight and restrictions on production uses took effect. The FDA, in agreements with pharmaceutical manufacturers, removed over-the-counter access to livestock-use antimicrobials that are in drug classes shared with human medicine as well as removed permission to administer those drugs through feed or water for growth, efficiency, or other production indications.
Agency officials had announced the upcoming changes in December 2013, stating that pharmaceutical companies would have three years to consent to the changes or face administrative action. All the affected companies had agreed to the changes by June 2014.