Health
Drug withdrawal intervals
By Karen Martin, VMD
Jul 22, 2003, 17:29

I am wondering how many of you have been informed by your veterinarians that there are withdrawal intervals on antibiotics and xylazine and some of the other drugs that you may be using.

Traditionally in food animals like cattle, veterinarians and farmers have been acutely aware of the fact that drug testing is going on in slaughter plants. The drugs that we use take variable amounts of time to be cleared from an animal’s body after they are injected or ingested. The FDA has set acceptable levels of drugs in tissue that are intended for human food. For some drugs like chloramphenicol there are no acceptable levels. This drug is not permitted for use in animals intended for human food. For other drugs like gentamicin, the withdrawal interval is at least one year or 454 days. The reasons for this are complicated, but have to do with humans eating the meat from these animals. If humans eat meat from animals that have drugs in their tissues, they can have allergic reactions. If people eat meats with low levels of antibiotics in them, the antibiotic can later become ineffective for use in humans.

All of the drugs that you use should have a withdrawal interval printed on the label. It should inform you of the amount of time that should elapse from the time that the drug is used to the time that the animal is killed for food. For example, if you use Xylazine to tranquilize an animal, the withdrawal interval is 14 days. You would not want any person to kill the animal until 14 days from the time the drug was used. Fourteen days is also the withdrawal interval for Yohimbine. For drugs used on species for which a withdrawal interval is not known, the withdrawal interval is 45 days. This includes Telazol. The time from injection of Telazol to the time that the meat should be used for food is 45 days because studies have not been done to determine how long it would take for the drug to be metabolized or leave the animal’s body.

If drugs are found in an animal’s body at slaughter, the veterinarian who prescribed the drug and the person who used the drug can end up being investigated by the FDA. If you are sending animals for slaughter for human food, you need to be very careful about drug use.

I have been getting a lot of questions about these issues recently, so I thought I would try to explain it to you all and ask for your feedback.


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