Antimicrobial Therapeutics Administered Via WaterAntimicrobial therapy can be administered via drinking water. Addition of ammonia to raise the pH of water may increase the solubility of some antimicrobials, such as sulfonamides and penicillin. Addition of organic or inorganic acid to lower water pH may increase the solubility of some classes of antimicrobials (eg, tetracyclines and erythromycin) when used via water application. In all cases, federal and state laws must be followed. For more information on compounding, visit the AVMA website. Any combination of antimicrobials would be subject to extralabel drug use rules as described in 21 CFR 530.13 (extralabel use from compounding of approved new animal and approved human drugs).Feed-Grade Antimicrobial TherapeuticsPoultry veterinarians have the option to administer in-feed medications. Combinations of FDA-approved in-feed medications that have obtained cross-clearance are limited. However, if in-feed antimicrobials are considered, the appropriate feed-grade antimicrobial must be used per the FDA-approved label indication. Extralabel drug use of in-feed antimicrobials is not permitted under any commercial conditions.Veterinarians are limited in their use of therapeutic antimicrobials in-feed based on FDA regulations published in the Code of Federal Regulations (21 CFR) and veterinary feed directive drugs section of the Animal Drug Availability Act of 1996. On December 11, 2013, the FDA finalized Guidance for Industry #213, establishing procedures for phasing out growth promotion indications for medically important antimicrobials in alignment with Guidance for Industry #209 and proposed changes to VFD drug regulations. The FDA CVM will assess progress made by drug sponsors after a 3-year period. All feed-grade antimicrobials may continue to be used as they are currently, at least until that time. The VFD regulation mandates the rules and responsibilities of licensed veterinarians in prescribing and administering medically important antimicrobials in feed. Guidance for Industry #209 establishes 2 principles: use of medically important antimicrobial drugs in food-producing animals should be limited to uses considered necessary for assuring animal health and use of medically important antimicrobial drugs in food-producing animals should include veterinary oversight or consultation. This would mean a change from over-the-counter to VFD regulation status for medicated feed products containing medically important antimicrobial drugs. Veterinarians should be involved in decisions regarding antimicrobial use in food animals for the health of the animal. No poultry in-feed medications currently require a VFD. Use of all medicated feed articles and combinations in poultry require following the FDA-approved label completely as extralabel drug use is not permitted. Veterinarians can refer to specific disease therapeutic strategies in this document to assess the potential benefit of approved feed-grade antimicrobials. Injectable Antimicrobial TherapeuticsInjectable antimicrobials are used predominately at 1 day of age or in ovo to control omphalitis in chicks and poults. In ovo administration to prevent infection when the yolk is withdrawn into the body cavity can be an important intervention strategy to control early bacterial contamination. However, appropriate sanitation and temperature controls must be maintained from breeder farm through the hatchery to minimize of the need for antimicrobials at 1 day of age and in ovo. Injection strategies should be used to support ongoing hatchery sanitation and proper egg collection techniques and not in lieu of these procedures. Current antimicrobials cleared for use in 1-day-old chicks or poults are not approved for use in ovo, and therefore, extralabel drug use regulations must be followed. The use of cephalosporins at unapproved dosages, frequencies, durations or routes of administration) is prohibited; therefore, in ovo use in chickens and turkeys is no longer permitted. Injectable antimicrobials are occasionally used in an extralabel manner, except for the cephalosporin class, for acute disease outbreaks in valuable and long-lived poultry. Fowl cholera and erysipelas can be treated in this manner. Antimicrobials used in this manner include long-acting oxytetracycline, florfenicol, and penicillin. With any such extralabel administration, extralabel drug use regulations must be followed.Further ReadingFor further details on treatment of specific disease in poultry, please refer to references below.
For a complete and current list of all the products affected by Guidance for Industry No. 213 and VFD drug regulations refer to the CVM's website. This is a public document. The VFD regulations and Guidance for Industry No. 213 were published in the Federal Register on December 12, 2013. The original listing of medically important antimicrobials can be found in Appendix A of Guidance for Industry No. 152 but is now superceded by Guidance for Industry No. 213.
Table 1 - Classes of antimicrobials approved for use in poultry
Table 2 - Classification of poultry antimicrobials approved for use in poultry, by human medical importance (FDA CVM Guidance for Industry No. 152)
Table 3 - Medically important antimicrobials based on FDA CVM Guidance for Industry No. 152 (now superceded by Guidance for Industry No. 213) and also delineated by the medical importance classification of antimicrobial products in regard to their human medical importance.
The intent of the categorizations is to restrict the use of medically important antimicrobials in animals to particular indications—particularly use in animals intended for food—while ensuring that sufficient therapeutic alternatives remain available to treat sick animals.