Elimination kinetics of tilmicosin following intramammary administration in lactating dairy cattle.
OBJECTIVE
To determine elimination kinetics of tilmicosin in milk following intramammary administration in lactating dairy cattle.


METHODS
Prospective pharmacokinetic study.


METHODS
6 lactating dairy cows.


METHODS
Following collection of baseline milk samples, 1,200 mg (4 mL) of tilmicosin was infused into the left front and right rear mammary glands of each cow. Approximately 12 hours later, an additional 1,200 mg of tilmicosin was infused into the left front and right rear glands after milking. Milk samples were then collected from each gland at milking time for 40 days. Concentration of tilmicosin was determined by means of ultraperformance liquid chromatography-mass spectrometry, and a milk withdrawal interval for tilmicosin was calculated on the basis of the tolerance limit method.


RESULTS
Although there was considerable variation between glands, concentration of tilmicosin was high in milk from treated glands and had a long half-life in treated and untreated glands. Tilmicosin was detected in all treated glands for the entire 40-day study period and was detected in untreated glands for approximately 30 to 35 days.


CONCLUSIONS
Findings indicated that tilmicosin should not be administered by the intramammary route in lactating dairy cows. Milk from all glands of any cows accidentally treated should be discarded for a minimum of 82 days following intramammary administration.
Smith
Geof W
GW
Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, USA.
Davis
Jennifer L
JL
Baynes
Ronald E
RE
Yeatts
James L
JL
Barlow
Beth M
BM
Riviere
Jim E
JE
D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods / Q000662:veterinary; D004350:Drug Residues / Q000032:analysis*; D005260:Female; D007263:Infusions, Parenteral / Q000662:veterinary; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008414:Mastitis, Bovine / Q000188:drug therapy* / Q000378:metabolism; D008657:Metabolic Clearance Rate; D008892:Milk / Q000737:chemistry*; D011446:Prospective Studies; D015645:Tylosin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000032:analysis / Q000493:pharmacokinetics
D000900:Anti-Bacterial Agents; C052319:tilmicosin; D015645:Tylosin