It is near impossible to overestimate the potential damage that intestinal parasites do to horses. Prior to development of the modern dewormers of the late 70's you could safely say that the length of horses' life spans were limited by that damage, particularly large strongyle larvae migration. The dewormer that changed this was ivermectin and it's ability to kill migrating larvae. For the first time we were able to actually control the exposure of horses to parasite larvae. This article addresses ivermectins characteristics, toxicity, and dosage. For information about total deworming programs see, Overview of Deworming.

Ivermectin belongs to the groups of avermectin anthelmintics. It is an off-white to yellowish powder that is very poorly soluble in water (4 micrograms/ml), but will dissolve in propylene glycol, polyethylene glycol, and vegetable oils.

Ivermectin is sensitive to light so should be protected from it. Ivermectin is stable at room temperature. Store up to 86 degrees F (30C). Transient exposure to temperatures up to 104F (40C) is permitted.