Sometimes new drugs are found in unusual places. The antiparasitic drug ivermectin was discovered in the 1970s in bacteria isolated from the soil on a Japanese golf course. Ivermectin was called the first "endectocide" since it was active against both endoparasites (parasites that live inside the host) and ectoparasites (parasites that live on the outside of the host).
Ivermectin was initially developed as a veterinary antiparasitic drug. Of particular importance today is ivermectin's ability to prevent heartworm infections in dogs with monthly dosing (e.g., Heartgard). Ivermectin has also protected hundreds of millions of livestock from a variety of parasites.
Ivermectin lotion is approved by the FDA for the treatment of head lice. Unlike many other treatments for head lice, ivermectin lotion only needs to be applied once. When given orally, ivermectin can be used for treating head or pubic lice and scabies (an itchy, highly contagious skin disease caused by mites burrowing in the skin). Oral ivermectin is useful to control outbreaks of scabies in nursing homes where whole-body application of topical agents is difficult.
Ivermectin's greatest impact on human health has been in Africa. Since 1987, in addition to its use for other parasitic infestations, ivermectin has been used extensively to control onchocerciasis with 1.4 billion treatments so far. Onchocerciasis is also called "river blindness" because the blackfly that transmits the disease breeds in fast-moving streams and rivers. Once within the body, the adult female worm produces thousands of juvenile worms that migrate to the skin and eyes and can produce severe itching and eye injury that can lead to blindness.
Ivermectin kills the juvenile worms, but not the adult females. The effectiveness of the drug lasts up to 12 months, but mature female worms produce offspring for 15 years, so ivermectin has to be taken once a year for that long.
Over 300 million people take ivermectin each year. Most adverse reactions are mild and temporary, such as loss of appetite, headache, muscle aches, lack of energy, and fever. There have been a small number of severe adverse events and even some deaths in humans treated with ivermectin in onchocerciasis-control programs. The reason for these events is unknown, but they might be linked to the presence of large numbers of other parasites that are killed off in treated patients.
If you suspect someone has swallowed ivermectin, do not make the person vomit. Immediately check the webPOISONCONTROL® online tool for help or call Poison Control at 1-800-222-1222.
When ivermectin gets in the eyes, minor irritation and redness can occur. Serious eye injury is not likely, but the eyes should be rinsed immediately. Remove contact lenses and use lots of room temperature water. For children, pour water onto the bridge of the nose and let it gently run into the eyes. Encourage blinking. After rinsing, call Poison Control or use the webPOISONCONTROL tool for help.
Mary Elizabeth May, RN, BA, MPH
Certified Specialist in Poison Information
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