By Ashley Steel, Contributing Writer and Dr. Melanie McLean, Senior Writer/Editor, Communications, Dr. Kevin Greenlees, Senior Science Advisor, Office of New Animal Drug Evaluation, Dr. Martine Hartogensis, Deputy Director, Office of Surveillance & Compliance
Correctly medicating animals is sometimes tricky. It requires a proper diagnosis and responsible veterinary treatment. Correctly medicating food-producing animals, such as cows, pigs, and chickens, is especially tricky. These animals provide us with food products like meat, milk, and eggs, and as the saying goes, “We are what we eat.”
When a food-producing animal is treated with a drug, chemical residues of the drug may be present in or on food products made from that animal. Chemical residues include small amounts of leftover drug, or parts of the drug that are not completely broken down by the animal’s body.
FDA’s CVM makes sure the chemical residues that may be present in or on food products made from treated animals pose little risk to people. By looking at information about the drug, CVM toxicologists determine the “acceptable daily intake,” or “ADI.” The ADI is the largest amount of the drug that will not harm people if they ingest that amount every day.
Using the ADI, CVM residue chemists set the tolerance for the drug, which is the level of chemical residues allowed to be in or on food products made from treated animals. Eating food that contains even the full amount of chemical residues allowed by the tolerance will not exceed the ADI. Based on the tolerance, the residue chemists set the withdrawal time. The withdrawal time is the time from when the animal was last treated with the drug to when the animal can be slaughtered for food or the animal’s milk can go to market. The withdrawal time allows for the drug (or parts of the drug) in the edible tissue of the treated animal to get to levels that are at or below the tolerance. If the withdrawal time is followed, food products made from a treated animal are safe for people to eat.
A drug that takes longer to get to the tolerance has a longer withdrawal period. Also, while there is only one tolerance for a given drug in a specific animal tissue (for example, cattle liver), the same drug may have different withdrawal times depending on how the drug is used, how it is given, or what type of food the treated animal produces. For example, the withdrawal time for a drug given to beef cattle (which provide us with meat) may be longer or shorter than the withdrawal time for the same drug given to dairy cattle (which provide us with both meat and milk). Similarly, an injectable form of a drug may have a different withdrawal time than the same drug given in another form, such as orally in medicated feed.
If a drug is used in an extra-label (“off-label”) manner in a food-producing animal, a veterinarian must be involved and is responsible for establishing an appropriate withdrawal time.
Selling food products containing levels of chemical residues above the set tolerances is illegal because such levels may harm people who eat that food. Both over-the-counter and prescription drugs can cause chemical residue levels to be above the set tolerances. To avoid illegal residues and to keep food products safe, CVM reminds veterinarians and animal producers to follow the withdrawal time for every drug they use in food-producing animals. CVM also asks animal producers to “T.A.L.K. before you treat.”
T - Talk to your veterinarian. Always check with your veterinarian before giving any drug to your animals.
A - Ask if the drug is approved by FDA for use in your animals. FDA’s approval means the drug is safe and effective when it is used according to the label. FDA’s approval also ensures that the drug’s strength, quality, and purity are consistent from batch to batch, and that the drug’s labeling is appropriate and truthful.
L - Look at the label. Know what drug you are giving and the dosage regimen. Be aware of the withdrawal time for the dosage regimen you are using. The dosage regimen includes:
- How much of the drug to give (the dose);
- How often to give it (the frequency);
- How long to give it (the duration); and
- How to give it (the route of administration). Various routes of administration include injecting the drug under the skin, into muscle, or into a vein; giving the drug by mouth; or applying the drug topically to the skin.
K - Keep complete treatment records. Good record-keeping will help you avoid illegal chemical residues because you will know:
- Which animals were treated;
- What drug they were treated with;
- How they were treated (the dosage regimen used);
- Why they were treated; and
- When it is safe for food products made from treated animals to enter the food supply.
T - Talk to your veterinarian.
A - Ask if the drug is FDA-approved.
L - Look at the label.
K - Keep complete treatment records.