Ivermectin

Ivermectin is an antiparasitic medication in the avermectin class, used in humans and animals to treat a range of parasitic infections. It was developed from the soil bacterium Streptomyces avermitilis and introduced for medical use in the 1980s. It exerts its effects by binding to glutamate-gated chloride channels in the nerve and muscle cells of many invertebrates, leading to increased chloride permeability, paralysis, and death of the parasite. Mammals are relatively protected because ivermectin poorly crosses the blood–brain barrier in humans.

In humans, ivermectin is approved for onchocerciasis (river blindness) and strongyloidiasis, and is used for crusted (Norwegian) scabies and, in some regimens, lymphatic filariasis. It is not active against protozoa such as Plasmodium species or bacteria; it is not a general antiparasitic for all infections.

Administration and pharmacokinetics: it is usually given as an oral tablet with weight-based dosing; topical formulations (1% cream or lotion) are available for head lice and some scabies cases. After administration, it is absorbed and extensively metabolized in the liver, and excreted mainly in feces; the drug is a substrate of P-glycoprotein.

Safety and special considerations: ivermectin is generally well tolerated at licensed doses. Adverse effects can include itching, rash, or fever related to dying parasites; more serious events can occur with overdose or certain co-infections, such as heavy parasitemia. It can interact with other drugs that affect P-glycoprotein transport. It should be avoided in pregnancy unless clearly needed; it is excreted in breast milk, so use during lactation requires consideration. In some dog breeds (collies), sensitivity to ivermectin can be increased.

Regulatory context: not approved for COVID-19; major health agencies do not support routine use for this purpose based on current evidence.