In December 2013, the U.S. Food and Drug Administration took steps to eliminate the use of antibiotics in food animals for growth promotion. It asked drug companies to do two things: remove indications for "feed efficiency" and "weight gain" from the labels of their antibiotic products and require veterinarians to oversee any addition of these drugs to feed and water. FDA’s new policy, known as Guidance for Industry #213, is intended to reduce antibiotic misuse, which contributes to the spread of antibiotic-resistant bacteria. Gaps in FDA's policy, however, may allow some injudicious practices to persist.

The Pew Charitable Trusts reviewed the labels of all 287 antibiotic products identified as being affected by Guidance #213 and looked for instances in which there was overlap between dosages approved for growth promotion and disease prevention. (See the full methodology below.)

Findings and analysis

Many antibiotics approved for disease prevention purposes were also approved for growth promotion. (See Figure 1.) In fact, about a quarter of the drugs (66 of 287) can be used in at least one species of livestock (chickens, turkeys, pigs, or cattle) for disease prevention at levels that are fully within the range of growth promotion dosages and with no limit on the duration of treatment. FDA classifies 29 of these 66 antibiotics as critically important in human medicine, and 37 as highly important.

The lines between disease prevention and growth promotion are not always clear. For example, 26 drugs approved for disease prevention are labeled to include "maintain[ing] weight gain" in the presence of vague illnesses, such as "respiratory disease." FDA does not consider this use to be for growth promotion despite the reference to weight gain. As a result, Guidance #213 allows drugmakers to continue using this ambiguous language on their products’ labels.