The Use of Aminoglycoside
Antibiotics In The Bovine
By Dr. Jacob Hines
American Association of Bovine Practitioners

In 1993, the Academy of Veterinary Consultants (AVC) adopted a resolution which stated that, "Until further scientific information becomes available alleviating the safety and efficacy concerns, Aminoglycoside antibiotics should not be used in cattle except as specifically approved by the Food and Drug Administration (FDA)."

Subsequently, the National Cattlemen’s Association (NCA) adopted the AVC’s position regarding the use of Aminoglycoside antibiotics.

Concerns identified by AVC regarding Aminoglycoside usage were that:

1. There were no published clinical studies justifying that extra label parenteral 1 use of Aminoglycosides in cattle;

2. Residues are known to be present in tissues for long periods of time when these drugs are used parenterally;

3. There exists a lack of pharmaceutical and toxicological data concerning the use of gentamicin and neomycin in cattle.

Recognizing the class of bovines with which the two endorsing organizations deal, it is reasonable to anticipate that the concern over Aminoglycosides is focused on the extra label "parenteral" 1 use of these antibiotics.

The following table is provided for the reader’s information.

AMINOGLYCOSIDE ANTIBIOTICS

Narrow Spectrum: FDA Approved Uses in Bovines:

Streptomycin none

Dihydrostreptomycin intramammary

Broad Spectrum:

Amikacin none

Gentamicin none

Kanamycin none

Neomycin oral and topical

There clearly is no FDA-approved parenteral use of Aminoglycoside antibiotics in the bovine. Therefore all use of this class of antibiotics falls under the FDA Compliance Policy Guide (7125.06) which deals with the extra label use of NADA 2 drugs in food producing animals.

As a point of fact, in 1992 a withdrawal of the NADA for the drug containing a combination of penicillin and Dihydrostreptomycin was issued. Since this drug is no longer FDA approved, inventories must be exhausted by June 1994. After that date it is illegal to use the combination and if such products are found on dairy farms, the farm will be in violation of the FDA Grade A Pasteurized Milk Ordinance (PMO). This infraction impacts PMO items 16r (i) which provides a 7 point deduction on the Grade A milk inspection report. The usage of either Dihydrostreptomycin and streptomycin alone has diminished markedly in recent years. The reasons are because of the limited spectrum of activity, the high degree of resistance by bacteria to these two drugs, and since there never existed an NADA for Dihydrostreptomycin and streptomycin, these products alone are also no longer available.

To Aminoglycosides, neomycin and gentamicin, when used parenterally, are of primary concern from the food safety standpoint. It is known that when used parenterally, both drugs can cause residues in kidney tissue for exceeding long periods of time. In the case of gentamicin, it has been reported that a residue of the drug may last as long as 18 months. Interestingly, it is suspected that on occasion, urine from animals treated with gentamicin may be negative to the LAST Test (Bacillus subtillis disk assay), but there may still exist detectable levels of this antibiotic in the parenchyma of the kidney.

When given orally, the molecular size of this class of drugs impedes appreciable absorption from the gut. In fact, there is an FDA NADA which allows for the use of gentamicin in the oral form for scours in baby pigs.

The administration of Aminoglycosides by the intratracheal and intravenous route in young calves as a treatment for pneumonia has been reported. The impact of this method of treatment on food safety has not been defined. It must be recognized however that this form of therapy would be performed on animals at an age that should preclude considerations of food safety.

The problem now facing the industry is the availability of legal drugs that are highly effective in treating a large number of infectious agents, but when used in an extra-label manner result in residues of these drugs in the tissues for long periods of time.

Undoubtedly, the FDA is not going to withdraw these drugs in the present form they are produced, because if used according to the label instruction, they are effective and safe.

It is possible that the FDA could add to the PMO restrictions prohibiting specific Aminoglycosides on dairy farms, but this would do little to decrease the use as long as the drug is legally available.

I do believe that our LCI Cattle Health Management Group can have an impact on the industry by passing a resolution stating that Aminoglycoside antibiotics should not be used parenterally in cattle.

1 Parenteral. For purposes of discussion in this paper, the term shall mean the administration by injection in any of the following routes: intramuscular, subcutaneous, intravenous, or intratracheal.

2 NADA is defined as a Food and Drug Administration New Animal Drug Application.