Ivermectin is an anti-parasite medication and is effective against most common intestinal worms (except tapeworms), most mites, and some lice. While normally used to treat animals, it is also prescribed to humans to treat infections of Strongyloides stercoralis and onchocerciasis (river blindness). It is sold under brand names Stromectol® in the United States and Mectizan® in Canada by Merck.

Ivermectin is chemically related to the insecticide avermectin, the active ingredient in some home-use ant baits. Both ivermectin and avermectin are derived from the bacterium Streptomyces avermitilis and kill by interfering with the target animal's nervous system.

In General Use Pesticide (GUP) formulations, these compounds are classified by the United States' Environmental Protection Agency as toxicity category IV, or very low. This means that although highly poisonous to insects, mammals should not generally be adversely affected by normal use of avermectin pesticide formulations. As an example, one such formulation was determined to have an oral LD50 (semi-lethal dose) of 650 mg/kg in rats (qualifies as toxicity category III—low toxicity) ^*. Extrapolated to an 80 kg (180 lb) human, this semi-lethal dose is 52g (1.9 oz), or an amount of the pesticide equal to about four dominoes, which is considered by the EPA to be a low toxicity amount.