IVERMECTIN IN DAIRY-COW - PLASMA-CONCENTR ATIONS AND MILK RESIDUES

Plasma and milk ivermectin disposition were studied in 6 dairy cows du ring lactation following the subcutaneous administration of 0.1 ml of the marketed formulation (Ivomec Bovins, MSD) i.e., about 2 mug/kg. Iv ermectin concentration (H2B1 a fraction) was analysed using an HPLC me thod with a level of quantification of 0.010 ng/ml. The maximal plasma concentration (0.46 +/- 0.20 ng/ml) was observed the first day follow ing administration; the mean maximal milk concentration (0.27 +/- 0.16 ng/ml) was observed at the 2nd sampling (day 3). The mean milk/plasma ratio was 0.48 +/- 0.18 and the recovered ivermectin amounts in milk ranged between 0.6% and 3.8% of the administered dose. Taking into acc ount the admissible daily intake of ivermectin (60 mug in toto) and th e other possible ivermectin intakes, it was concluded that ingestion o f milk from cow treated with 0.1 ml of the marketed ivermectin formula tion was of no concern with regard of milk residues.