WASHINGTON – Three US Senators say the Food and Drug Administration's plan to curb antibiotic use in food-animal production may not be not be effective.

In a 
July 28 letterto FDA Commissioner Margaret Hamburg, Sens. Dianne Feinstein, Elizabeth Warren and Kirsten Gillibrand detailed their concerns about the FDA's plan for animal-pharmaceutical companies to voluntarily phase-out the use of antibiotics in food-production animals. The letter follows a recent federal appeals court ruling that the FDA is not required to withdraw approval for animal drugs the agency itself deems unsafe.

"We are pleased that the Food and Drug Administration has taken an important for step to address how the overuse of antibiotics in food animal production contributes to antibiotic resistance, but we remain concerned that the FDA's recently released policies do not go far enough," the legislators wrote. "We seek additional information about how the FDA plans to evaluate whether these new policies are successful in curbing the overuse of antibiotics in food animal production and what additional actions FDA plans to take if this overuse continues."

In a final guidance issued Dec. 11, 2013, the FDA laid out a plan for animal-pharmaceutical companies to voluntarily revise the FDA-approved use conditions on the labels of products to remove such production indications as “growth promoting,” etc. The plan also calls for changing the current over-the-counter status to bring the remaining appropriate therapeutic uses under veterinary oversight and requiring a prescription for use.

The lawmakers noted that requiring veterinary oversight of antibiotic use in food animals is an important step in curbing overuse of antibiotics. But that requirement doesn't go far enough.

"Oversight by veterinarians alone, however, will not solve the problem if the FDA continues to approve antibiotics regimens that allow for continuous, low-dose use to prevent and contain disease," they said.

The FDA said the agency will respond directly to the legislators’ request for information.