US FDA seeks input on time limits for therapeutic use of antibiotics in feed

Specific antimicrobials that are also medically important for humans and that do not currently have set timelines for usage as a treatment or preventative for certain diseases in production animals are being reviewed, the agency said.

“The Food and Drug Administration is soliciting comments regarding the establishment of appropriately targeted durations of use of antimicrobial drugs of importance to human medicine when they are administered in the feed or water of food-producing animals for therapeutic purposes,” ​the agency said. “This activity is consistent with previous efforts by FDA to protect public health by promoting the judicious use of these drugs in food-producing animals.”​

The agency posted its request for feedback​​ on Wednesday. The comment period is open through December 13.

“FDA will consider submitted comments as we develop a process by which sponsors of currently approved, medically important antimicrobial drugs, administered in feed or water to food-producing animals for therapeutic purposes, could establish appropriately targeted durations of use,”​ the agency said. “We recognize that, in certain circumstances, some medically important antimicrobial drugs may have a range of safe and effective durations. Approval of defined durations of use may be supported by existing effectiveness data, target animal safety data, human food safety studies, clinical pharmacology studies, disease pathophysiology, and/or other available information.”​

Judicious use efforts​

The agency has established the Veterinary Feed Directive (VFD) to address judicious use of antibiotics in production animals. The rule, which goes into effect on January 1 2017, limits medically important antimicrobial drugs to uses in food-producing animals that are considered necessary for assuring animal health and restricts the application of such drugs to uses that include veterinary oversight or consultation. 

The goal of the current initiative, said the FDA, is to establish a “dosage strategy that maximizes drug effectiveness, minimizes target animal toxicity, and has the appropriately targeted duration of use to minimize the development of resistance to antimicrobial drugs of human medical importance."​ 

The agency is looking for comments from swine, poultry and cattle producers and veterinarians on when animals are most at risk for developing certain diseases; what husbandry practices might limit the need for an antimicrobial to be fed or for how long it would need to be used and thoughts on ways to address labeling.

It also is asking typically what the duration of use is of such drugs, how that duration was established, what possible benefits or problems could come from defining a use period and what other alternatives might be available instead of the antimicrobial.

In poultry, the antimicrobials being discussed include ormetroprim with sulfadimethoxine; lincomycin; virginiamycin; oxytetracycline and hygromycin B, which can be used to address challenges such as chronic respiratory disease, necrotic enteritis, fowl cholera, coccidiosis, infectious coryza and gastrointestinal parasites.

Cattle products being reviewed include chlortetracycline, oxytetracycline, tylosin, virginiamycin and neomycin with oxytetracycline, the agency said. They are used to control anaplasmosis, bacterial enteritis, liver abscesses and pneumonia.

Swine producers face the possibility of restricted time period uses for tylsin; tylosin with sulfamethazine; chlortetracycline; sulfamethazine; oxytetracycline; hygromycin B; lincomycin; chlortetracycline with sulfamethazine; chlortetracycline, when given to address atrophic rhinitis, pneumonia, GI-parasites or bacteria or jowl abscesses, the agency said.