Analytical tools for prudent and effective drug use

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On July 6, 2012, the USDA Food Safety and Inspection Service (FSIS) announced the launch of new analytical methods and sampling procedures for the United States National Residue Program (NRP) for Meat, Poultry, and Egg products [Docket No. FSIS-2012-0012] (9 CFR Parts 417).

click image to zoomMilk and other fluid samples such as urine collected from animals prior to slaughter could be used to assess if edible tissues are fit for human consumption if these assays are appropriately validated. Here, Sheila Tuftee from the ISU-VDL prepares samples for drug screening by LC-MS. As part of the restructuring process, the FSIS is implementing several multi-residue methods (MRM) for analyzing samples of meat, poultry, and egg products for animal drug residues, pesticides, and environmental contaminants in its inspector-generated testing program. The new MRM being implemented by the FSIS is reported to provide significant improvements to the previously imple mented testing strategy, including:

• It can screen for a variety of analytes, not just antibiotics.

• The method can be validated at levels appropriate in relation to tolerances.

• Because of the power of mass spectrometry, it can clearly distinguish individual analytes, even if multiple drugs are present in the same sample.

• Unknown microbial inhibition responses would be mitigated.

• The time and personnel needed to obtain results is reduced.


click image to zoom There are 52 analytes appropriate for inclusion in the new MRM at and above the level specified (see Resources box). The MRM and the aminoglycoside method will replace the 7-plate bioassay and the KIS™ test as an initial screen test in the laboratory. The FSIS estimates a four-workday turnaround for negative samples and that that the new confirmation process for KIS-positive samples could take between three and 10 days, depending on the number of residues detected on any one sample, the number of tissues tested, and the type of confirmation or quantification required.

What motivated the changes?

The FSIS is making the changes to the NRP to:

• Identify emerging contaminants

• Prevent adulterated meat, poultry and eggs from entering the market place

• Discourage improper behavior by producers, processors and importers

• Close regulatory gaps between Agencies

What are the implications for bovine practitioners?

• The FSIS is now testing for prednisone, gamithromycin, sulfanilamide, sulfanitran, and beta-dexamethasone, which were not tested for previously. There is no tolerance established for many of these compounds that now are included in the test—most notably, dexamethasone. This raises significant questions about how the discovery of residues will be interpreted and enforced. It also gives practitioners the additional responsibility of ensuring that treated animals are free of any residues when consigned for human consumption. Sensitive and specific antemortem tests that correlate with tissue depletion profiles in cattle are needed to assist practitioners in making these decisions.

• The MRM methods are significantly more sensitive than the 7-plate bioassay used previously for the majority of analytes. This increases the probability of residue detection, even at very low levels.

• The FSIS expects the number of violations to increase (especially in cull dairy cows), even though the total number of samples tested will decrease.

• In many cases, the analytical sensitivity of the MRM is significantly lower than the established tolerance or “safe level” for many of the compounds currently used in cattle which may create challenges with respect to interpreting the results.

Antibiotics milk panel also available

In 2012, the Iowa State University Veterinary Diagnostic Laboratory established the Cyclone Custom Analyte Detection Service (CYCADS), which offers a research-focused pharmacology presence unmatched at any other veterinary diagnostic laboratory in the United States. CYCADS provides professional services characterized by accurate analysis of batch research samples with a commitment to a short turnaround time.

In March of 2012, CYCADS launched an antibiotics milk panel (see Bovine Veterinarian July 2012), which includes multiple classes of antibiotics, several NSAIDs, and some anthelmintic drugs, for a total of 41 drugs in the panel.

Among the classes of drugs measured are four beta-lactams (penicillins), two cephalosporins (plus two ceftiofur metabolites), four tetracyclines, eight sulfonamides, four macrolides, two lincosamides, two phenicols, and several other compounds, including flunixin, a flunixin metabolite, meloxicam, tripelennamine, and ractopamine. The drug panel also includes anthelmintic drugs such as thiabendazole and three macrocyclic lactones (i.e., ivermectin).

Hans Coetzee is with Veterinary Diagnostic & Production Animal Medicine and the CYCADS section leader at Iowa State University. Locke A. Karriker, DVM, MS, ACVPM and Joshua Ellingson, DVM, Iowa State University, also contributed to this report.

 

References

1. Federal Register Vol. 77, No. 130. New Analytic Methods and Sampling Procedures for the United States National Residue Program for Meat, Poultry, and Egg Products. 9 CFR Parts 417. [Docket No. FSIS–2012– 0012]. Available at: http://www.fsis.usda.gov/oppde/rdad/FRPubs/2012-0012.pdf. Accessed October 10, 2012.
2. Almanza, A. Administrator, FSIS. Letter to Southwest Meat Association. Available at: www.fsis.usda.gov/PDF/RD_2012-0012.pdf. Accessed October 10, 2012.

3. Bennett, P. Office of Public Health and Science. FSIS. Patty.Bennett@FSIS.USDA.gov. Available at: http://foodrisk.org/irac/events. Accessed October 10, 2012.

4. Meiszberg A, Karriker L, Zimmerman J, Irwin C, and Coetzee J. 2011. Detection of ceftiofur and oxytetracycline in oral fluids of swine with a pen-side competitive ELISA test after intramuscular injection.

J Vet Pharmacol Ther Oct;34(5):515-7. doi: 10.1111/j.1365–2885.2010.01259.x. Epub 2010 Dec 28.


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