Just to offer a little more insight on FDA’s inaction, discussed broadly in a previous blog, I’ve detailed the history of just one of the antibiotic additives in question here.
Penicillin G Procaine 50/Penicillin 100 (NADA:046-666) is an antibiotic feed additive and as good an example as any of FDA’s failure to protect public health (see the report for references). The drug is approved for use for growth promotion and increased feed efficiency in pigs, chickens, and turkey and continues to be marketed in spite of risks to human health. Here are the details:
In the early 1970s, the drugmaker (“sponsor”) submitted an application for an antibiotic additive containing Penicillin G procaine and also submitted plans for scientific studies to show antimicrobial safety, to respond to safety regulations put in place by FDA in 1973. In their review, FDA scientists noted not only that the studies that were eventually submitted and linked to the application had flaws -- meaning that they were poor evidence for the additive’s safety -- but also that some of the studies actually showed evidence of increased antimicrobial resistance to other antibiotics from the use of this additive. For example, in two separate studies, the sponsor observed that “[f]eeding penicillin supplemented diets significantly increased the number of E. coli resistant to chloramphenicol” and to “ampicillin,” respectively. In their 2003 scientific review, the FDA scientists indicated that, based on the evidence in the record, the agency’s 1973 safety criteria had never been met.
Later, FDA scientists assessed the safety of the additive against current safety guidelines, finalized in 2003. Based on the information before them, they estimated that the use of this antibiotic additive in animal feed presents a high risk to human health in its current use in livestock and poultry.
After this internal scientific review was conducted, in 2004, FDA sent a letter to the drugmaker outlining FDA’s concerns that the additive promotes antibiotic resistance and its assessment that the additive likely poses a high risk to human health. The FDA documents contain no new evidence from the sponsor to address FDA’s concerns and yet FDA has taken no action to withdraw approval. The additive remains approved for use and is being marketed today.
As a microbiologist, the details in the record raise some red flags for me. Studies showing resistance to other antibiotics in the same class (ampicillin) or in a different class (chloramphenicol) mean that feeding Penicillin G procaine was leading to potential cross or co-resistance and endangering the efficacy of other antibiotics. Given those observations and the assessment that the use of the additive in animal feed likely poses a high risk, it’s difficult to understand why no action was eventually taken.
FDA should be moving aggressively to protect public health. Antibiotics are a key element of modern human medicine and keeping them effective for curing sick people requires us to also address overuse and misuse of antibiotics in animal agriculture.