Scabies is caused by the mite Sarcoptes scabiei burrowing into the upper layer of human skin. It affects an estimated 200 million people worldwide at any moment, and the intense night-time itch is an allergic reaction to the mite, its eggs and its waste. Oral ivermectin is one of the two first-line treatments recommended internationally, and it is the treatment of choice when topical therapy is impractical, has failed, or when an outbreak needs to be controlled across a household or institution.
Ivermectin binds with high affinity to glutamate-gated chloride ion channels found in invertebrate nerve and muscle cells. Binding increases membrane permeability to chloride ions, hyperpolarising the cell and causing paralysis and death of the parasite. Mammals do not have these glutamate-gated chloride channels in the peripheral nervous system, and ivermectin does not readily cross an intact blood-brain barrier, which is the basis of its wide safety margin in humans.
Because ivermectin does not reliably kill mite eggs, a single dose leaves viable eggs that hatch over the following week. This is why every current protocol uses two doses spaced 7 to 14 days apart — the second dose kills the newly hatched mites before they can mature and lay again.
The established regimen for classical scabies is 200 micrograms per kilogram of body weight, taken orally, repeated after 7 to 14 days. For a 70 kg adult that is roughly 14 mg per dose — commonly given as tablets totalling that amount.
Absorption increases substantially when ivermectin is taken with food. Several pharmacokinetic studies have found bioavailability roughly doubles with a high-fat meal compared with fasting, which is why many clinicians now advise taking it with a meal rather than on an empty stomach.
A Cochrane systematic review of interventions for scabies found that oral ivermectin and topical permethrin both achieve high cure rates, with permethrin showing a modest advantage at the first follow-up and the two converging by later assessment. Trials consistently report cure rates in the region of 85 to 95 percent after two doses of oral ivermectin.
Where ivermectin has a clear practical advantage is compliance and outbreak control. A single supervised oral dose is far easier to administer correctly across a family, a care home or a school than a whole-body topical application that must be left on overnight and repeated. Mass drug administration studies in the Pacific have demonstrated dramatic community-level reductions in scabies prevalence using ivermectin.
Crusted scabies is a severe form in which the host mounts a poor immune response and mite numbers reach the hundreds of thousands or millions, producing thick hyperkeratotic crusts. It is extremely contagious and is the usual source of institutional outbreaks.
Treatment is more intensive: oral ivermectin is typically given on days 1, 2 and 8 for moderate cases, with additional doses on days 9, 15, 22 and 29 in severe cases, combined with a topical scabicide and keratolytic therapy to break down the crusts so the drug can reach the mites. Australian and CDC guidance both describe multi-dose regimens of this kind.
Ivermectin has an established safety record in this indication. The most common adverse effects are mild and transient: headache, dizziness, nausea and a temporary worsening of itch as mites die and release antigen. Serious neurological events are rare at standard doses.
Itching frequently continues for two to four weeks after successful treatment. This is post-scabetic pruritus — an ongoing allergic response to residual mite material in the skin — and it is not evidence that treatment failed.
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View products and pricingYes. Two oral doses of 200 mcg/kg given 7 to 14 days apart cure the great majority of classical scabies cases, with trial cure rates typically between 85 and 95 percent. The second dose is essential because ivermectin does not kill mite eggs.
Mites are killed within days, but itching commonly persists for two to four weeks afterwards as an allergic reaction to residual mite material. Persistent itch alone is not a sign of treatment failure. New burrows or new lesions after four weeks may indicate reinfestation or a resistant case.
Cure rates are broadly comparable. Cochrane review data give topical permethrin a small edge at early follow-up, with results converging later. Oral ivermectin is generally preferred where topical application is impractical, for institutional outbreaks, and for crusted scabies, mainly because a supervised oral dose is far easier to administer correctly.
Yes. Standard guidance is to treat all household members and close physical contacts at the same time, whether or not they have symptoms, because the incubation period means contacts can be infested and contagious for weeks before itching begins.