The U.S. Food and Drug Administration (FDA) has urged Bayer A.G. to remove the drug Baytril from the market on the grounds that its use as an animal antibiotic may eventually compromise the ability of Cipro, also a Bayer product, to fight anthrax and other diseases in people.

Baytril, which is used to treat infectious disease in poultry, is chemically similar to Cipro, with both products belonging to a class of drugs known as fluoroquinolones, among the most powerful antibiotics currently on the market. Hence the concern by FDA, doctors and consumer groups that widespread use of Baytril to treat infections like campylobacter in poultry will cause disease germs to become resistant to closely related drugs like Cipro.

At press time, the manufacturer, veterinarians and members of the poultry industry all voiced opposition to the withdrawal of Baytril, indicating that its danger to human health had not been proved. Farmers say they will have to change their poultry-raising practices and could lose millions of dollars if the drug is withdrawn.

Bayer officials issued a statement that Baytril poses "no public health threat" and that "there's no evidence that withdrawal of the product would either resolve or have a meaningful impact on the number" of infections with resistant germs in humans.

This isn't the first time that FDA and Bayer have butted heads over Baytril. Last year, FDA recommended banning use of the drug and another fluoroquinolone antibiotic, sarafloxacin, in poultry. According to the New York Times, FDA made the request after studies suggested that resistant camplyobacter germs in humans had increased to more than 17 percent since the introduction of fluoroquinolones to treat poultry four years before. The Times reported that Saraafloxacin manufacturer Abbott Laboratories agreed to remove the drug from the market, but that Bayer refused to pull Baytril.

Bayer officials maintain that more proof is needed that the use of antibiotics in animals can be blamed for increased resistance in people. FDA must decide whether there is enough evidence supporting its position to warrant a full hearing.