Ivermectin
Ivermectin is a macrocyclic lactone medicine used to treat parasitic infections. It is effective against infections with:
- Parasitic worms including: onchocerciasis (river blindness), strongyloides, cutaneous larva migrans and filiariasis
- Ectoparasites, including scabies
In New Zealand, Ivermectin is available in 3mg tablets (Stromectol™). The medicine is covered by Section 29 of the Medicines Act – which means it is not registered in New Zealand. It is available on prescription but full details of the prescription are required to be reported to the Minsitry of Health by the supplier.
Ivermectin has been used extensively as part of the World Health Organisation's Onchocerciasis Eradication Program. It has FDA approval for the treatment of strongyloides and onchocerciasis in the United States, other use is termed ‘off label’.
In treatment of scabies its use may be appropriate in selected cases where topical therapy is impractical or has failed and is particularly useful in cases of crusted scabies (also called ‘Norwegian’ scabies).
How does it work?
Ivermectin stimulates excessive release of neurotransmitters in the peripheral nervous system of parasites. It is thought to work by paralysing the parasite or inactivating the parasite gut. In humans the neurotransmitters acted on by ivermectin are in the brain. A protective barrier, called the blood-brain barrier, blocks ivermectin from reaching the human brain.
How is it taken?
Ivermectin is taken as a single dose with a glass of water. It is rapidly absorbed from the gut and metabolised in the liver.
| Infestation | Dose regime |
|---|---|
| Onchocerciasis | Single dose of 150mcg/kg (may be repeated every 3 to 12 months) |
| Strongyloidiasis | Single dose of 200mcg/kg |
| Scabies | Dose of 200mcg/kg repeated in 7 to 14 days |
| Cutaneous larva migrans | Single dose of 200mcg/kg |
Side effects
Side effects are rare and usually minor. These include:
- Transient tachycardia (fast heart rate)
- Flushing
- Nausea
- Lightheadedness
- In treatment of onchocerciasis; fever, rash, muscle or joint aches and tender glands and eye irritation/swelling or pain
- In treatment of strongyloidiasis; diarrhoea, skin rash
- More severe neurological side effects are theoretically possible in rare susceptible individuals
The safety of ivermectin in pregnant women has not been studied and such use is not recommended. Studies in animals have shown an increase in birth defects. Safety and effectiveness in children under 15kg has not been established. Ivermectin passes into breast milk and use during breast feeding is not recommended.
Drug interactions
No significant drug interactions are recognised.
Related information
On DermNet NZ:
References
- Bolgnia J L, Jorizzo J L, Rapini R P. Dermatology 2003, Elsevir Limited
- Elgart G W, Meinking T L. Ivermectin. Dermatologic Clinics 2003; 21: 277-82
Other websites:
- Ivermectin Medline Plus
- Ivermectin – MedlinePlus
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