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[Pharmacology](https://durgical.com/en/pharmacology/) · [Anthelmintics](https://durgical.com/en/pharmacology/classes/anthelmintics/)

# Ivermectin

Single-dose oral avermectin: the drug of choice for strongyloidiasis and onchocerciasis; it opens chloride channels found only in invertebrates.

Updated 2026-11-01

- Class: [Anthelmintics](https://durgical.com/en/pharmacology/classes/anthelmintics/)
- Ion channel: Nematode glutamate-gated chloride channel (GluCl)
- ATC code: P02CF01
- WHO Model List of Essential Medicines

⇅**Nematode glutamate-gated chloride channel (GluCl)**Ivermectin

ⓘ The figure shows ivermectin bound to the GluCl channel of Caenorhabditis elegans, a free-living nematode; it is the same channel family that parasitic worms have and humans lack.

**Target in 3D:** Nematode glutamate-gated chloride channel (GluCl). PDB structure 3RHW (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3RHW) · Drag to rotate · pinch to zoom

## Mechanism of action

It binds glutamate-gated chloride channels in invertebrate nerve and muscle and holds them open. Chloride flows in, the cell hyperpolarises and the worm is paralysed and dies. It also acts on GABA-gated chloride channels. In humans P-glycoprotein at the blood-brain barrier keeps it out of the brain, which explains its safety.

- Binds GluCl channels in worm nerve and muscle
- The channel stays open and chloride flows in
- The cell hyperpolarises: paralysis
- The worm or microfilaria dies

## Pharmacokinetics

**Absorption**
Oral, on an empty stomach with water; a fatty meal greatly raises bioavailability

**Distribution**
Very lipid-soluble; P-glycoprotein keeps it out of the brain; little passes into milk

**Metabolism**
Liver, mainly by CYP3A4

**Elimination**
Almost all in faeces; under 1 % in urine

**Half-life**
About 18 hours

**Onset and duration**
Peak blood level about 4 hours after the dose

## Indications

- Intestinal strongyloidiasis (drug of choice) and, with repeated dosing, hyperinfection [Strongyloidiasis →](https://durgical.com/en/conditions/strongyloidiasis/)
- Onchocerciasis (kills microfilariae, not adult worms)
- Scabies (used in some cases) [Scabies →](https://durgical.com/en/conditions/scabies/)
- Head and pubic lice (used in some cases) [Pediculosis (head, body and pubic lice) →](https://durgical.com/en/conditions/pediculosis/)

## Adverse effects

### Common

- Dizziness and itching
- Nausea, diarrhoea and abdominal pain
- Mild rise in transaminases and low white cells
- In onchocerciasis, the Mazzotti reaction: itching, fever, joint pain, swollen lymph nodes, oedema and tachycardia
- Orthostatic hypotension

### Serious (rare, important)

- Severe or fatal encephalopathy in people with heavy Loa loa in the blood
- Neurotoxicity: confusion, disorientation, seizures and coma
- Toxic epidermal necrolysis and Stevens-Johnson syndrome
- Hepatitis and worsening asthma

## Contraindications

- Hypersensitivity to ivermectin
- Pregnancy (safety not established)
- Confirmed or suspected Loa loa infection (relative)
- Impaired blood-brain barrier, such as meningitis

## Key interactions

**Warfarin**
Rare reports of raised INR

**Levamisole**
Raises ivermectin levels

## What is monitored

- Serial stool exams after Strongyloides treatment to confirm eradication
- Screening for Loa loa before treating anyone who has been in endemic areas of West or Central Africa
- Blood pressure and Mazzotti symptoms in onchocerciasis
- INR in patients on warfarin
- Level of consciousness

## Administration and safety

- Oral, on an empty stomach with water; usually a single dose that is sometimes repeated.
- Human products only: the FDA warned against self-treatment with veterinary products.
- Immunocompromised patients may need repeated courses and cure may not be achievable.
- Safety has not been established in children under 15 kg.

## Nursing care

- Before starting corticosteroids or immunosuppressants in people from endemic areas, think of Strongyloides: hyperinfection can be fatal.
- In onchocerciasis: get up slowly (orthostatic hypotension) and watch for fever, itching and joint pain in the first days.
- Report blurred vision, severe headache, confusion, drowsiness, seizures or trouble walking.
- Teaching: complete the follow-up stool tests; report pregnancy or breastfeeding.

## Pregnancy and breastfeeding

The label says it should not be used in pregnancy because safety has not been established; WHO excludes pregnant women from mass campaigns. Small amounts pass into milk.

## Memory aid

IVERmectin «IVERy chloride»: opens GluCl and paralyses the worm; beware Loa loa and Mazzotti; take fasting.

## Test yourself

Think of the answer, then tap the question to see it.

## What is ivermectin's target in worms?

Glutamate-gated chloride channels (GluCl) in nerve and muscle, which humans lack.

## Why does ivermectin barely affect the human brain?

Because P-glycoprotein at the blood-brain barrier pumps it out.

## What serious risk does ivermectin carry in a person with Loa loa?

Severe or fatal encephalopathy when Loa loa microfilaraemia is heavy.

## What is the Mazzotti reaction?

An inflammatory reaction to dying microfilariae in onchocerciasis: itching, fever, joint pain, lymph nodes and oedema.

## Why does ruling out Strongyloides before corticosteroids matter?

Because corticosteroids can trigger severe hyperinfection; ivermectin is the treatment.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/pharmacology/ivermectin/)

## Related drugs

- [Albendazole](https://durgical.com/en/pharmacology/albendazole/)
- [Praziquantel](https://durgical.com/en/pharmacology/praziquantel/)

## Related conditions

- [Strongyloidiasis](https://durgical.com/en/conditions/strongyloidiasis/)
- [Scabies](https://durgical.com/en/conditions/scabies/)
- [Pediculosis (head, body and pubic lice)](https://durgical.com/en/conditions/pediculosis/)

[← Back to the class: Anthelmintics](https://durgical.com/en/pharmacology/classes/anthelmintics/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - IVERMECTIN tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=847a1dd7-d65b-4a0e-a67d-d90392059dac) (DailyMed (U.S. National Library of Medicine), 2026); [Ivermectin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a607069.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [Clinical Care of Strongyloides](https://www.cdc.gov/strongyloides/hcp/clinical-care/index.html) (Centers for Disease Control and Prevention (CDC), 2024); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 68 (McGraw Hill, 2023).

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Representative model, for educational purposes only.

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