December 4, 2012

The Honorable Margaret Hamburg, Commissioner U.S. Food and Drug Administration 10903 New Hampshire Ave. Silver Spring, MD 20993

Dear Commissioner Hamburg:

We are writing to inform you of the results of new tests of pathogens and of ractopamine levels in pork products appearing in the January, 2013 issue of Consumer Reports, to urge the U.S. Food and Drug Administration (FDA) to prohibit the use of antibiotics in livestock except for treatment of disease, and to revoke approval for use of ractopamine in pork.

I. Ractopamine

Consumer Reports tested some 240 pork products for ractopamine, a drug used in pork, beef, and turkey production to promote weight gain and enhance feed efficiency. Very low, but detectable, levels of ractopamine between 1 and 5 parts per billion (ppb) were found in about one-fifth of the samples tested for the drug. Although the ractopamine levels in the samples we tested were significantly below FDA’s Maximum Residue Level (MRL) of 50 parts per billion (ppb), we strongly disagree with the safety assessment that led to this MRL and agree with the European Union (EU) that no MRL can be set for ractopamine given the present data.

As you know, in December 1999, FDA approved ractopamine hydrochloride (Paylean, NADA 140-863) for use in finishing pigs. In 2012, using a six volunteer human study, the Codex Alimentarius Commission voted to adopt a much lower MRL of 10 ppb. The EU and China, however, both considered the available studies inadequate to set an MRL and so prohibit the use of ractopamine.

We believe the FDA MRL should be reconsidered. We do not think ractopamine meets the FDA safety standard of “safe and effective for a specific use in a specific animal species … [and] that food made from animals treated with the drug is safe for people to eat.”1 FDA based their MRL for ractopamine on a study done in rhesus monkeys, in which the agency determined it showed a no-observed-effect level (NOEL) of 125 ?g/kg-bw.2 In choosing the NOEL from the rhesus monkey study, we believe that FDA ignored important data for setting safety limits from a dog study and a human study in the same NADA (e.g. NADA 140-863). The dog study determined a NOEL of 2 ?g/kg-bw, while the human study had a NOEL of 99 ?g/kg-bw.3 Further, the NOEL for humans, i.e., 99 ?g/kg-bw, was based on an overall/composite value for the three cardiac function variables tested, not the NOEL for the most sensitive variable, the cardiac output, for which the NOEL was 83 ?g/kg-bw. We strongly believe that using an average or composite value for a NOEL, rather than the lowest NOEL, contradicts the meaning/purpose of a NOEL, thereby making it not be a true NOEL. In other words, the NOEL for rhesus monkeys was more than 60-times higher than the value for dogs, and some 50 percent higher than the most sensitive NOEL for humans. Thus, we do not think that FDA used the most sensitive species (dog) when developing their MRL for ractopamine in pig tissue. We are aware that FDA’s rationale for not using the most sensitive species, e.g. dog, was that the rhesus monkey 24-hour clearance rate for an oral dose of ractopamine via urine was closer to that of humans compared to dogs, e.g. 42% and 45% versus 54%, respectively, and that FDA “concluded that the primate model is more predictive of the human acute toxicity response to oral exposure to RACT [ractopamine] than the canine model.”4 However, we believe that the difference in clearance rates is small and does not justify a failure to base the standard on the most sensitive species, i.e. dogs. We also question why FDA had human data, yet chose to base its standard on monkey data for which there was a higher NOEL than provided by the human data.

For the complete letter, click here (PDF format)

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