August 01, 2004


 Gentamicin sulfate, sulfamethoxazole used illegally

Posted July 15, 2004

The Food and Drug Administration has recently issued warning letters to veterinarians for their illegal use of gentamicin sulfate and sulfamethoxazole.

For example, a veterinarian prescribed and compounded a product containing sulfamethoxazole for extralabel use in lactating dairy cattle. Sulfamethoxazole is prohibited for extralabel use in lactating dairy cattle. In addition, the compounded product also contained dexamethasone, but the label did not list this as an ingredient.

Veterinarians have also mishandled gentamicin sulfate. In one instance, a veterinarian prescribed and dispensed gentamicin sulfate for extralabel use in a dairy cow without providing a label that established an adequate withdrawal period, supported by required scientific information. In another, a veterinarian prescribed gentamicin sulfate products including compounded products containing the drug, and was not able to support the labeled withdrawal interval with scientific information.

Prior to prescribing or dispensing an approved animal drug for an extralabel use in food animals, a veterinarian must make a careful diagnosis and evaluation of the condition for which the drug is to be used, establish a substantially extended withdrawal period prior to marketing an edible product, institute procedures to ensure that the identity of the treated animal is carefully maintained, and take appropriate measures to ensure that assigned timeframes for withdrawal are met. This includes specifying a withdrawal/discard time on a drug label for any food that might be derived from a treated animal.

In addition, the FDA has not approved gentamicin for use in cattle or scientifically established a withdrawal time for cattle. While the Food Animal Residue Avoidance Databank recommends a minimum preslaughter withdrawal period of 18 months or more for this drug, the AVMA and American Association of Bovine Practitioners have called on veterinarians to avoid extralabel use of aminoglycosides, including gentamicin, in cattle, because of the propensity for these drugs to be retained in kidney tissue for long periods.

To obtain a copy of the "FDA and the Veterinarian" booklet and "Extralabel Drug Use" brochure, free of charge, call the AVMA at (800) 248-2862, Ext. 6636.