FARAD: The Food Animal Residue Avoidance and Depletion Program
One of the regulatory requirements for legal ELDU is that the attending veterinarian recommend a scientifically based withdrawal interval before the producer can market the milk, meat, eggs, or other edible products.
Commonly, the most efficient way for a food animal practitioner to meet these requirements is to consult FARAD. Veterinarians, producers, students, or regulatory personnel may obtain free consultation with specialists by contacting 1-888-US-FARAD or accessing the FARAD website at http://www.farad.org and submitting a request. Recommendations are made on a case-by-case basis depending on the individual variables of each exposure, changing tolerances or FDA withdrawal times, and new information in the literature. FARAD also advises on pesticide exposure and accidental contaminations (biotoxins, heavy metals, radionuclides, unintended feeding of medicated feed).FARAD maintains a database of all food animal products approved in the United States, with thousands of pharmacokinetic citations describing depletion for numerous chemicals in various species. The FARAD website now has a portal for searching what citations are included in the FARAD bibliographic database. FARAD collects, analyzes, and evaluates scientific data to provide withdrawal intervals when drugs are used in an extralabel manner. The FARAD website contains a database of approved food animal drugs searchable by drug, trade name, and species, known as VetGRAM (http://www.farad.org/vetgram/). A mobile version of VetGRAM is also available on the FARAD website. Veterinarians may also find downloadable copies of published summary recommendations as well as a quick review of past recommendations there.
Published techniques for estimating a withdrawal interval (WDI) after ELDU in food animals are available.14-16 Information that FARAD considers when estimating a WDI includes the following:
1.
General factors affecting pharmacokinetic parameters and drug residues, such as conditions affecting drug absorption and elimination as well as dose, duration of treatment, and administration route.2. Existence of an FDA-established withdrawal time. AMDUCA stipulates that a substantially extended withdrawal should be applied for any ELDU. Therefore doses that are less than the labeled dose will still require a withdrawal that is longer than the labeled WDT.
3. Physiologic factors and compromised health conditions affecting pharmacokinetic parameters and drug elimination (e.g., dehydration, renal dysfunction, gastrointestinal disease).
4. Published pharmacokinetic parameters (i.e., time versus concentration data, including drug residue serum, tissue, or milk data).
5. The existence of an established tolerance or maximum residue limit (MRL).
6. Analytical testing method and limits of detection.
7. Foreign drug approval data.
Testing for Drug Residues
If a practitioner or producer/owner wants to confirm that edible products (i.e., meat or milk) are at or below the tolerance, they can consider testing for drug residues. A number of commercial rapid tests exist for drug residue testing using a milk, serum, or urine matrix. Examples of manufacturers of these tests include IDEXX Laboratories, Inc.; Charm Sciences; DSM Food Specialties; Neogen Corporation; and Silver Lake Research Corporation. Care should be taken to ensure that the test used detects residues to a level at or below the FDA- established tolerance to be certain that the food product is safe to enter the human food chain. Alternatively, samples or
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carcasses can be submitted to a commercial laboratory or state veterinary diagnostic laboratory for residue testing. Processing plants may be willing to test milk. FDA-established tolerances can be found on the FDA animal drugs website or FARAD's VetGRAM website.
Regulatory Monitoring of Drug Residues in Animal Products
Once products begin the process of entering the human food chain, they may undergo residue testing as part of the National Residue Program (NRP). The FSIS, EPA, and FDA cooperate to regulate animal drug residues, pesticides, environmental contaminants, and any other chemical hazards in meat or egg products. Every year, the sampling plan, known as the “Blue book,” is released, which includes such details as the number of tissue or egg samples that will be tested and which chemical or drug residue will be tested for. Results of the testing are also made publicly available on an annual basis in the “Red book.”
After remaining unchanged for many years, in July 2012, FSIS announced that scheduling of the NRP sampling plan will be changing.17 Sample numbers per production class will be reduced because of the adoption of new analytical methods. Analysis for more chemical residues per sample will be possible, requiring fewer overall samples than in the past.