Description
Ivermectol (ivermectin)
Ivermectin is one of the most important antiparasitic drugs in existence — on the WHO list of essential medicines, responsible for nearly eliminating river blindness in several African countries, awarded the Nobel Prize in 2015 for the work that led to its development. It treats a specific category of infections very effectively. It does not treat COVID-19, viral infections, or bacterial infections. Understanding which category your problem falls into determines whether this drug will help you at all.
Available in 3 mg, 6 mg, 9 mg, and 12 mg tablets.
What it actually treats
Strongyloidiasis (threadworm infection), onchocerciasis (river blindness), scabies, head lice, cutaneous larva migrans, and several other parasitic infections affecting the skin, intestinal tract, and eyes.
The mechanism is specific to parasites: ivermectin binds to glutamate-gated chloride channels found in parasite nerve and muscle cells, causing paralysis and death. Human cells don’t have these channels, which is why therapeutic doses are well-tolerated in most people.
Dosing — weight-based
The standard dose is 200 micrograms per kilogram of body weight. Not a fixed tablet number — weight-based. A 70 kg person takes roughly 12 mg; a 90 kg person takes 18 mg.
For strongyloidiasis: a single dose is usually sufficient. Follow-up stool tests confirm eradication.
For scabies: two doses are standard — the initial dose plus a second dose 1 to 2 weeks later. Severe or crusted scabies may follow a more intensive schedule (days 1, 2, 8, 9, and 15) and typically requires concurrent topical treatment with permethrin 5%.
For river blindness: repeated dosing every 6 to 12 months, as the drug kills microfilariae (larval stage) but not adult worms.
Take ivermectin tablets on an empty stomach with a full glass of water — one hour before or two hours after meals. Food significantly increases absorption and can lead to higher-than-intended blood levels.
The Mazzotti reaction
When parasites die in large numbers, the immune response to their breakdown products can cause a cluster of symptoms: fever, chills, joint and muscle pain, headache, swollen lymph nodes, rapid heartbeat, rash, intense itching. This is called the Mazzotti reaction and is not a drug allergy — it’s a sign the treatment is working. It’s most pronounced in onchocerciasis. Knowing this in advance prevents unnecessary alarm or premature discontinuation.
Side effects
Common: temporary dizziness or lightheadedness, mild stomach discomfort, nausea, diarrhea, temporary rash or itching, headache, swollen lymph nodes. Most are mild and transient.
Serious but less common: severe skin reactions with blistering or peeling, visual disturbances or eye pain, significant changes in blood pressure or heart rate, difficulty breathing or swallowing, seizures, or neurological symptoms. These require stopping the drug and seeking medical attention.
Contraindications
Hypersensitivity to ivermectin. Children under 5 years old or under 15 kg for oral formulations. Pregnancy — the safety profile in pregnancy is insufficient; most guidelines recommend avoiding it unless the infection risk clearly outweighs the unknown fetal risk. Breastfeeding: small amounts appear in breast milk; discuss with a prescriber. Significant liver disease.
Drug interactions: warfarin and other blood thinners (ivermectin may enhance anticoagulant effects), CNS depressants, and drugs affecting the GABA system.
What it doesn’t treat
Viral infections including COVID-19. Bacterial infections. Multiple large randomized controlled trials have found no benefit for ivermectin in COVID-19 treatment or prevention. Neither the FDA nor WHO recommends it for this use outside of clinical trials. Veterinary ivermectin formulations — regardless of the COVID claims that circulated online — are formulated for animal body weights and contain concentrations that have caused serious overdose in humans.
