Ivermectin sold under brand names Stromectol® in the US and Mectizan® in Canada. It is a 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).

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 as EPA 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) [1]. Extrapolated to a 80 kg (180 lb) human, this semi-lethal dose is 52 g (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.

However, pure avermectin formulations are both highly toxic to insects and mammals (as well as aquatic life, such as fish). One study reports an oral LD50 of 10 mg/kg in rats (qualifies as toxicity category I--high toxicity) [2].

External links

• Ivermectin for human use
• Site profiling ivermectin and avermectin as pesticides
• Toxicity information for avermectin

References

• U.S. National Library of Medicine. Hazardous Substances Databank. Bethesda, MD, 1995.10-9
• Lankas, G. R and Gordon, L. R. Toxicology. In Ivermectin and Abamectin. Campbell, W. C., Ed. Springer Verlag, New York, NY, 1989.10-142
• U.S. Environmental Protection Agency. Pesticide Fact Sheet Number 89.2: Avermectin B1. Office of Pesticides and Toxic Substances, Washington, DC, 1990.10-143