FDA warns against use of unapproved aspirin in lactating dairy cattle

The Food and Drug Administration (FDA) is informing veterinarians and farmers to stop using unapproved aspirin to treat pyrexia and pain in lactating dairy cattle.

The nonsteroidal anti-inflammatory drug is being used on some dairy farms to treat cattle infected with highly pathogenic avian influenza (HPAI, more specifically avian influenza type A H5N1), according to a communication from the American Association of Bovine Practitioners (AABP) to its members.

The FDA published a “Dear Veterinarian” letter on October 11 as a reminder and educational effort that the extralabel use of unapproved drugs in food-producing species is prohibited.

“The U.S. Food and Drug Administration understands that veterinarians and dairy farmers may be treating lactating dairy cattle for pyrexia and pain with aspirin and wants to clarify that there are no FDA-approved aspirin products for use in cattle,” the letter states. “There are FDA-approved products for controlling pyrexia and pain in lactating dairy cattle that are safe, effective, and have established milk and meat withdrawal periods.”

Flunixin is FDA-approved for the control of pyrexia associated with bovine respiratory disease, endotoxemia, and acute bovine mastitis; the control of inflammation in endotoxemia; and the control of pain associated with foot rot.

In addition, Vazalore is the one FDA-approved human aspirin product that veterinarians may use in food-producing species under specific conditions, according to the Animal Medicinal Drug Use Clarification Act, also known as AMDUCA.

To allow extralabel drug use, a valid veterinarian-client-patient relationship must be established, an appropriate withdrawal time must be assigned, violative residues must not result, and only approved human or animal drugs may be used. AMDUCA says a veterinarian should not prescribe a drug in an extralabel manner if there is an approved drug that is labeled for the indication unless that labeled therapy is ineffective as determined by the veterinarian.

Because Vazalore is only available in 81 mg and 325 mg dosages, the FDA says veterinarians and dairy farmers may instead be using unapproved aspirin products, which come in larger dosages. Although other human aspirin products are marketed under an over-the-counter monograph, that monograph is not an approval and, therefore, these products cannot be used in an extralabel manner.

AABP leaders met with FDA’s Center for Veterinary Medicine for clarification on the extralabel use of aspirin.

“Previously, FDA has stated that aspirin use was of low regulatory concern; however, due to its increased use, questions from the public about its use, and the availability of labeled products for treatment of pyrexia (flunixin), they have shifted this stance to state such use is illegal,” according to an October 12 AABP announcement to its members.

As of October 21, H5N1 has been confirmed in dairy cattle in 14 states: 131 herds in California, 64 in Colorado, 33 in Idaho, 29 in Michigan, 26 in Texas, 13 in Iowa, nine each in Minnesota and New Mexico, seven in South Dakota, four in Kansas, two in Oklahoma, and one each in North Carolina, Ohio, and Wyoming.

“In the event that animals have already been treated with aspirin, veterinarians should use their scientific expertise and available resources to set protective and extended milk and meat withdrawal periods for treated animals,” according to the FDA letter.

A version of this story appears in the December 2024 print issue of JAVMA

Correction: An earlier version of this story incorrectly stated that flunixin has a drug label claim for "relaxed inflammation."