Wednesday, May 6, 2015

The Truth About the Withdrawal Period for Wazine

"The egg withdrawal period for Wazine is two weeks."  - Statement found on a Facebook chicken group posted on May 5, 2015.

The two-week Food and Drug Administration approved label withdrawal time for Wazine® is specifically for meat, not eggs, and only for chickens (and turkeys) to which the drug is administered according to label instructions. There are two main reasons why this withdrawal time cannot be directly extrapolated to eggs from backyard chickens.

1. The disposition of the active ingredients, i.e. the rate at which they distribute to and deplete from meat and eggs, may differ. This can result in higher drug concentrations in eggs, requiring a longer withdrawal time.

2. The length of a withdrawal time is proportional to the dose administered to the chicken (the higher the dose, the longer the withdrawal time needed).  The actual dose of Wazine® that a backyard chicken receives may be higher or lower than the dose on which the label withdrawal time is based. This is because the product is administered through the chicken’s water or food. When determining the label withdrawal time, the source and amount of water and food can be tightly controlled to ensure a specific dose. But backyard chickens can obtain food and water from different sources, and their intake varies depending on several physiological, environmental and behavioral factors.

The use of a product like Wazine® in backyard egg producing chickens constitutes extra label use, and should therefore occur under the guidance of a veterinarian, who is responsible for ensuring that the withdrawal time is adequately extended to account for differences in drug dose and disposition.

Answer provided by scientists at the Food Animal Residue Avoidance Databank (FARAD)