Pharmacokinetics of eprinomectin in plasma and milk following subcutaneous administration to lactating dairy cattle.
Eprinomectin is only available as a topically applied anthelmintic for dairy cattle. To determine whether eprinomectin can be applied as an injectable formulation in dairy cattle, a novel injectable formulation was developed and was subcutaneously delivered to four lactating dairy cattle at a dose rate of 0.2 mg/ kg. Plasma and milk samples were collected. The concentrations of eprinomectin in all samples were determined by HPLC. The peak plasma concentration (C(max))of 44.0+/-24.2 ng/ml occurred 39+/-19.3 h after subcutaneous administration, equivalent to the C(max) (43.76+/-18.23 ng/ml) previously reported for dairy cattle after a pour-on administration of 0.5 mg/kg eprinomectin. The area under the plasma concentration-time curve (AUC) after subcutaneous administration was 7354+/-1861 (ng h)/ml, higher than that obtained after pour-on delivery (5737.68+/-412.80 (ng h)/ml). The mean residence time (MRT) of the drug in plasma was 211+/-55.2 h. Eprinomectin was detected in the milk at the second sampling time. The concentration of drug in milk was parallel to that in plasma, with a milk to plasma ratio of 0.16+/-0.01. The highest detected concentration of eprinomectin in milk was 9.0 ng/ml, below the maximum residue limit (MRL) of eprinomectin in milk established by the Joint FAO/WHO Expert Committee on Food Additives in 2000. The amount of eprinomectin recovered in the milk during this trial was 0.39%+/-0.08% of the total administered dose. This study demonstrates that subcutaneous administration of eprinomectin led to higher bioavailability and a lower dose than a pour-on application, and that an injectable formulation of eprinomectin may be applied in dairy cattle with a zero withdrawal period.
Baoliang
P
P
College of Veterinary Medicine, China Agricultural University, 100094, Beijing.
Yuwan
W
W
Zhende
P
P
Lifschitz
A L
AL
Ming
W
W
D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002417:Cattle; D005260:Female; D006207:Half-Life; D007279:Injections, Subcutaneous; D007559:Ivermectin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics; D007774:Lactation; D008892:Milk / Q000737:chemistry*
D000871:Anthelmintics; D007559:Ivermectin; C101434:eprinomectin