Ivermectin

Ivermectin Tablets: A Practical Guide

Ivermectin belongs to the avermectins, a group of antiparasitic compounds first obtained from a soil bacterium. The scientists behind its discovery shared the 2015 Nobel Prize in Physiology or Medicine, and it appears on the WHO Model List of Essential Medicines. Donation and public-health programs deliver hundreds of millions of treatments every year against parasitic diseases in Africa, Asia and Latin America.

How Ivermectin Works

Worms and mites rely on a type of chloride channel in their nerve and muscle cells that mammals largely lack. Ivermectin binds tightly to these channels and holds them open, so the parasite becomes paralysed and dies. In people, a protective barrier normally keeps standard doses away from the brain, which is one reason correct, weight-based dosing matters so much.

What It Is Used For

Labeled uses

• Strongyloidiasis: an intestinal threadworm that can persist silently for decades and become life-threatening in anyone who later takes steroids or has weakened immunity.
• Onchocerciasis (river blindness): a filarial infection spread by blackflies that damages the skin and eyes.

Other established uses

• Scabies, especially crusted scabies, outbreaks or when creams are unsuitable. See our scabies guide.
• Lymphatic filariasis, given together with other medicines in community treatment programs. See our filariasis guide.
• Head lice, mainly as a topical lotion, with tablets occasionally used when other treatments have failed.

Strengths Available

Every brand contains the same active ingredient. Several tablets may be combined to reach the prescribed dose.

How It Is Dosed

Ivermectin is normally given as a single dose based on body weight, sometimes repeated:

• Strongyloidiasis: 200 micrograms per kg once. Stool tests are repeated afterwards to confirm the infection has gone.
• Onchocerciasis: 150 micrograms per kg once, repeated every 3 to 12 months as advised, because the medicine kills larvae (microfilariae) but not the adult worms.
• Scabies: 200 micrograms per kg, with a second dose 7 to 14 days later.

The product label advises taking the tablets on an empty stomach with water. Your prescriber may give specific timing instructions for your condition. Never take more than prescribed: an overdose can cause confusion, unsteadiness, seizures and coma.

Side Effects

Ivermectin is usually well tolerated at standard doses. When side effects occur they tend to be mild, such as dizziness, nausea, diarrhea, tiredness, itching or a rash.

People treated for onchocerciasis may develop a Mazzotti reaction within a few days as larvae die: itching, rash, fever, tender swollen glands, joint aches, swelling and dizziness on standing up. It usually settles, but tell your doctor.

Seek urgent medical help for confusion, marked drowsiness, difficulty walking or speaking, fits, fainting, or signs of an allergic reaction such as facial swelling or breathing difficulty.

Important Precautions

• Loa loa infection: people who have lived in parts of Central or West Africa may carry the African eye worm. Heavy infection increases the risk of a rare but serious brain inflammation (encephalopathy) after ivermectin, so testing is needed first.
• Pregnancy: not recommended. If you are breastfeeding, discuss it with your doctor.
• Children under 15 kg: safety has not been established.
• Warfarin: ivermectin may increase its effect, so extra INR checks may be needed.
• Liver disease or a weakened immune system may require closer follow-up or repeat courses.

Ivermectin and COVID-19

The World Health Organization and the US Food and Drug Administration do not recommend ivermectin to prevent or treat COVID-19, and large randomised trials found no meaningful benefit. The tablets in this category are intended only for parasitic infections.

Never use veterinary ivermectin. Pastes, drenches, pour-ons and injections made for horses, cattle, sheep or dogs are far more concentrated, contain ingredients not tested in people and have caused serious poisonings.

Frequently Asked Questions

Which strength do I need?

That depends on your weight and the condition being treated. Your prescriber calculates the total dose and the combination of tablets that reaches it.

Does ivermectin kill every stage of a parasite?

No. In filarial infections it mainly kills the larvae rather than adult worms, and in scabies it does not reliably kill eggs, which is why repeat doses or combination treatment are often needed.

Should I take it before traveling as a precaution?

No. It is not recommended as a routine preventive for travelers. Avoiding insect bites, taking care with food and water, and wearing shoes on soil are the key precautions.

This content is for general education only and cannot replace individual advice from a doctor or pharmacist. Ivermectin is a prescription medicine; take it only for a diagnosed parasitic infection and exactly as prescribed.