Levamisole residues in chicken tissues and eggs

Levamisole is currently being used to treat capillaria infection in chickens even though there is no published withdrawal information available for levamisole in chickens. Tissue residue withdrawal of levamisole in chickens was studied in 32 healthy broiler breeder chickens at the age of 32 wk (peak of egg production). Levamisole residues in chicken tissues, eggs, and plasma were determined by HPLC with ultraviolet (UV) detection at 225 nm. The highest level of residue and longest withdrawal after oral administration of 40 mg/kg levamisole to chickens was in the liver. On d 3 the level of levamisole were undetectable in the plasma. On d 9, levamisole residue in eggs was 0.096 microg/g and on d 18 it was 0.06 microg/g or less in all the analyzed chicken tissues. Those levels were lower than the recommended maximum residue limit (MRL). The withdrawal time for levamisole in chickens was longer than for other species tested, which is due in part to a larger dose of levamisole being recommended for chickens. In conclusion from this research, 9 d are needed for levamisole in eggs to be less than the MRL, and 18 d of withdrawal are needed before medicated birds are slaughtered if their tissues are to be safe for human consumption.