have a potent, broad antiparasitic spectrum at low dose levels. They are active against many immature nematodes (including hypobiotic larvae) and arthropods.

The macrocyclic lactones are well absorbed when administered PO or parenterally; the pour- on formulations exhibit greater variability. Regardless of the route of administration, macrocyclic lactones are extensively distributed throughout the body and concentrate particularly in adipose tissue

Effective levels are reached in the Gl system, lungs, and skin regardless of the route of administration