Pharmacokinetics of Eprinomectin in Plasma and Milk following Subcutaneous Administration to Lactating Dairy Cattle |
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Authors: | P Baoliang W Yuwan P Zhende A L Lifschitz W Ming |
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Institution: | (1) College of Veterinary Medicine, China Agricultural University, 100094 Beijing;(2) Biological Technique Limited Corporation, Beijing China Agricultural University, Beijing, China;(3) Area Farmacologia, Depto de Fisiopatologia, Facultad de Cs. Veterinarias, Tandil, Argentina |
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Abstract: | 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 (Cmax)of 44.0±24.2 ng/ml occurred 39±19.3 h after subcutaneous administration, equivalent to the Cmax (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. |
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Keywords: | eprinomectin injectable formulation pharmacokinetics subcutaneous administration withdrawal period |
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