abstract_textpIn a series of studies with ivermectin in cattle, we determined the drug concentrations in serum over time resulting from daily oral dosages at 50, 100, and 200 mu g/kg and from daily subcutaneous injections at 5, 20, and 80 mu g/kg. We also determined the profile of ivermectin in serum resulting from oral treatment at 75 mu g/kg at 3-d intervals. For cattle treated orally at the same dosage, a significant difference in the level of drug in serum was found between animals held on pasture and those held in indoor stanchions. In contrast, no difference in serum ivermectin was found in cattle held on pasture and those held in stanchion if they were treated by injection. A subsequent trial showed that the quantity of foodstuff consumed by the animal can account for some of the differences observed in cattle treated orally. A simple spreadsheet model was developed for estimating the level of ivermectin in serum over time. The results of these trials provide a useful database for the development of a variety of delivery systems for ivermectin in cattle./p/abstract_text
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