, eprinomectin, abamectin, doramectin, and moxidectin are variously available as PO, SC, and pour-on formulations for use in cattle. The SC and PO formulations are given at 0.2 mg/kg, whereas the pour-on formulation is used at 0.5 mg/kg. Pour-on formulations are more convenient but exhibit greater variability between animals compared with SC or po administration. Grooming behavior of cattle has a major influence on the plasma disposition of topical macrocydic lactones. Undesirable subtherapeutic concentra ons both treated and untreated cattle may contribute to development of drug resistanc .