Animal & Veterinary
TOLERANCES ESTABLISHED FOR TETRACYCLINES IN MILK
FDA Veterinarian Newsletter September/October 1998 Volume XIII, No V
The Food and Drug Administration (FDA) is amending the animal drug regulations to reflect approval of a supplemental new animal drug application (NADA) 113-232 filed by Pfizer Animal Health. The supplemental NADA provides for use of Liquamycin LA-200 (oxytetracycline) injection in lactating dairy cattle. Previously, Liquamycin LA-200 was approved for treatment of beef cattle, non-lactating dairy cattle, calves including pre-ruminating (veal) calves, and swine. The supplemental application for use in lactating dairy cattle and a new tolerance for tetracyclines residues in milk were approved by FDA on July 21, 1998.
With this supplementary approval, Liquamycin LA-200 now is labeled for administration to beef cattle, dairy cattle (including lactating dairy cattle), and calves, including pre-ruminating (veal) calves, for the treatment of pneumonia and shipping fever complex associated with Pasteurella spp. and Haemophilus spp., bovine keratoconjunctivitis (pink eye) caused by Moraxella bovis; foot-rot and diphtheria caused by Fusobacterium necrophorum; bacterial enteritis (scours) caused by Escherichia coli; wooden tongue caused by Actinobacillus ligniersii; leptospirosis caused by Leptospira pomona; and wound infections and acute metritis caused by strains of staphylococci and streptococci organisms sensitive to oxytetracycline.
Milk taken from animals during treatment with Liquamycin LA-200 and for 96 hours after the last treatment must not be used for food.
The tolerance for tetracyclines including oxytetracycline, chlortetracycline, and tetracycline are amended to provide for an acceptable daily intake (ADI) and for a tolerance for residue in milk. The Center for Veterinary Medicine (CVM) conducted a reevaluation of the toxicology and metabolism data that were used to support the original tolerance for oxytetracycline in edible tissues. The ADI for total residues of tetracyclines including chlortetracycline, oxytetracycline, and tetracycline, is 25 micrograms per kilogram of body weight per day. Sixty percent (60%) of the ADI is reserved for milk and 40% for edible tissues. Based on the ADI, a tolerance of 300 ppb is established for the sum of residues of the tetracyclines including chlortetracycline, oxytetracycline, and tetracycline in milk. With the establishment of a tolerance of 300 ppb for the sum of residues of tetracyclines, a tolerance of 300 ppb for each of the three tetracyclines is also established.
The previously accepted safe levels for oxytetracycline, chlortetracycline, and tetracycline in milk were 30, 30, and 80 ppb respectively for a sum of residues of 140 ppb. The FDA, States, and the dairy industry have regulated milk at these levels since 1991. With the change in tolerance to 300 ppb in milk, there are no longer any FDA accepted rapid screening tests for tetracyclines in raw co-mingled bovine milk. The FDA is currently working with Charm Sciences to modify their Charm II Tetracyclines Drug Test (Competitive) to detect residues at the new tolerance level. FDA encourages other sponsors of tetracyclines kits to submit performance data on the detection of residues of tetracyclines in milk to CVM for evaluation.
Further information about milk screening tests is available from Dr. Norris E. Alderson, FDA/Center for Veterinary Medicine (HFV-500), Office of Research, 8401 Muirkirk Road, Laurel, MD 20708, 301-827-8010. Further information about the tolerances for tetracyclines in milk is available from Dr. Margaret Miller, Center for Veterinary Medicine (HFV-100), Food and Drug Administration, 7500 Standish Pl., Rockville, MD 20855, 301-827-5282.