Ivermectin dosage, forms, and strengths

Ivermectin (brand name Stromectol) is an anti-parasitic medication used to treat various parasitic infections, including infections from parasitic worms, scabies, and lice. It is also available as a topical cream (brand name Soolantra) used to treat adult rosacea and an over-the-counter topical lotion (brand name Sklice) for head lice.

For most parasitic infections, ivermectin treatment is only needed for a short course and is dosed based on body weight. A single dose of ivermectin is typically between 0.15 and 0.25 mg/kg, given by mouth, to be taken on an empty stomach in tablet form. For some persistent conditions such as scabies, ivermectin use may be repeated several times for complete resolution. When treating scabies and lice, each oral dose of ivermectin should be taken with food, while doses for strongyloidiasis and onchocerciasis parasitic infections are taken on an empty stomach.

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Ivermectin forms and strengths

Ivermectin is available in the following forms and strengths:

• Tablet: 3 mg

• Lotion: 0.5% 

• Cream: 1% 

Ivermectin dosage for adults

Ivermectin has been approved by the Food and Drug Administration (FDA) for the oral treatment of intestinal parasites in the Strongyloides family and nematode parasites of the Onchocera family, as well as topical treatment of head lice and inflammatory pustules in rosacea. Without an FDA indication, oral ivermectin has also been useful for treating other intestinal parasites, scabies, and scalp and pubic lice in individuals who have failed or are not candidates for other treatments. Adult dosing varies by indication.

Ivermectin dosage for strongyloidiasis 

Strongyloidiasis is a condition that occurs from infection with the parasitic roundworm Strongyloides stercoralis. Parasitic larvae in contaminated soil penetrate human skin, migrate to the lungs via the bloodstream, and then climb up the airways to be swallowed down into the small intestines. There, the larvae mature into adult female worms, which lay eggs while embedded in the intestinal submucosa. Once these eggs hatch, new larvae can either be passed in the stool or can cause autoinfection by penetrating the intestines or anus. 

It is important to receive correct and timely treatment for strongyloidiasis as recurrent autoinfection may contribute to a more difficult-to-treat hyperinfection syndrome and dissemination of the worms throughout the entire body. Hyperinfection and dissemination can be extremely fatal, with a mortality rate close to 90%, and are more likely to occur in individuals receiving high-dose corticosteroids. For parasitic worms, ivermectin works by paralyzing the worms by blocking chloride channels in nerve and muscle cell membranes. 

For the treatment of strongyloidiasis in adults, oral ivermectin is administered as a single 0.2 mg/kg dose meant to be taken on an empty stomach.

Ivermectin dosage for onchocerciasis

Onchocerciasis is more commonly known as river blindness. It is a parasitic disease caused by the filarial worm Onchocerca volvulus. Repeated bites with infected blackflies transmit this worm from human to human. Once in the blood, these worms migrate to the skin, eyes, and lymphatic system, causing severe itching, disfiguring subcutaneous skin nodules, visual impairment including permanent blindness, and swollen lymph nodes. Ivermectin is the treatment of choice for onchocerciasis and could prevent blindness and reduce the occurrence and severity of skin symptoms when administered early. 

It is not uncommon for individuals with onchocerciasis to have a co-infection with the eye worm Loa loa. Of note, ivermectin should not be used for the treatment of onchocerciasis in these individuals due to serious side effects, as there is a risk of fatal encephalopathy from ivermectin facilitating the entry of the Loa loa parasite into the nervous system. 

Additionally, certain drugs used in the treatment of filariasis may cause a severe and potentially life-threatening systemic reaction known as the Mazzotti reaction. The use of ivermectin for onchocerciasis may result in individuals experiencing these adverse effects. 

In treating onchocerciasis in adults, oral ivermectin is administered as a single 0.15 mg/kg dose meant to be taken on an empty stomach. For resistant disease, this treatment may be repeated after three months. 

Ivermectin dosage for scabies 

Human scabies is a contagious, itchy skin condition caused by the human itch mite Sarcoptes scabiei. These microscopic mites burrow into the upper layer of the skin where they live and lay eggs. Scabies infestations are usually very itchy and accompanied by a pimple-like skin rash. A very severe form of scabies, known as crusted scabies, occurs in individuals with weakened immune systems or neurological diseases. Crusted scabies manifest with thick crusts of skin containing large numbers of scabies mites and eggs. 

Scabies is spread by prolonged, direct contact with another person who has scabies. Infestations are common in crowded institutes such as prisons and nursing homes. Ivermectin's efficacy in treating scabies is due to its ability to attack the mite’s nervous system, resulting in the mite's death. 

For non-crusted scabies in adults, ivermectin is given in a single dose of 0.2 mg/kg with food. If symptoms persist, this treatment may be repeated in two weeks. 

For crusted scabies in adults, ivermectin is given as a 0.2 mg/kg dose on days 1, 2, and 8, with doses on days 9 and 15 sometimes added. It is to be taken WITH food and used along with a topical scabicide. This course may continue to days 22 and 29 for extremely severe cases. 

RELATED: More scabies treatments and medications

Ivermectin dosage for lice 

Head lice are very common, with an estimated 6 to 12 million cases occurring each year in the United States among children 3 to 11 years of age, according to the Center for Disease Control (CDC). Infestations are caused by the bloodsucking parasite Pediculus humanus on the head and Pediculus pubis (also known as Phthiriasis pubis) in the pubic region. This parasitic insect pierces human skin and feeds on human blood. Unlike body lice, these live, breed, lay eggs, and eat while holding onto the hair shaft. Both are transmitted through contact.

In most adult cases of head lice, topical ivermectin 0.5% lotion can be applied to the head and scalp and left on for 10 minutes. Ivermectin interferes with lice's muscle and nerve functions, paralyzing and then killing them. 

In adult cases of refractory head or pubic lice, it can be dosed in tablet form, 0.2 mg/kg of body weight every 10 days for 2 doses for refractory head lice and 0.2 mg/kg of body weight every 1 to 2 weeks for 2 doses for refractory pubic lice. 

RELATED: FDA approves Rx-to-OTC switch for head lice lotion

Ivermectin dosage for rosacea

Rosacea is an immunologic and inflammatory facial skin condition resulting in redness, acne-like lesions, and flushing. It is a chronic condition, and treatments are available to control it but not cure it. Management aims to reduce the severity of facial lesions and the frequency of flushing.

The safety of ivermectin, as well as its efficacy in the treatment of rosacea, were analyzed in two randomized, double-blind, vehicle-controlled clinical trials. Negative side effects were reported in less than 1% of patients and included skin burning and skin irritation. The exact mechanism of action for ivermectin in the treatment of rosacea is unknown. However, some studies suggest that ivermectin exerts significant anti-inflammatory properties and effectively suppresses several pro-inflammatory cytokines.

For the treatment of rosacea in adults, ivermectin 1% cream is applied to the affected areas once a day before bedtime. 

Ivermectin dosage for children

In the pediatric population, with an FDA indication, ivermectin is used to treat worms and head lice. Off-label, it is prescribed for non-crusted scabies. In tablet preparations, ivermectin is dosed based on weight, to be administered to children weighing more than 15 kg (33 lbs). Treating onchocerciasis may require repeat doses every three to 12 months, and treating scabies may necessitate a second dose in two weeks. In treating head lice, ivermectin topical lotion can be used on children 6 months and older. 

Ivermectin dosage restrictions

Ivermectin is contraindicated and not to be used in the setting of prior hypersensitivity allergic reactions to the drug. In addition, it should not be used in individuals with loisasis co-infection. 

Of note, the FDA does not approve or approve ivermectin to treat COVID-19. Clinical trials did not support its use, leading the Infectious Diseases Society of America (IDSA) and the National Institutes of Health (NIH) to recommend against its use for the coronavirus. 

Ivermectin dosage for pets

Ivermectin is routinely used to treat parasites in animals. It is important to note that these preparations differ from those prescribed for humans, and humans should not take ivermectin that was prepared and prescribed for an animal. This medication is used in a highly concentrated form for both small and large animals, where therapeutic doses for animals could be toxic to humans. 

In cats and dogs, ivermectin is most commonly used to prevent heartworm and treat gastrointestinal or external parasites, ear mites, body mites, and scabies. It is typically given as a tablet, liquid, or injectable for use by a veterinarian. 

Ivermectin should be used with caution in some pet groups:

• Certain breeds, including collies, shepherds, and sheepdogs, have experienced toxic effects from ivermectin, especially at higher doses.

• Prior to beginning treatment with ivermectin for heartworm prevention, dogs need to be tested for existing heartworms.

• Ivermectin should be avoided in dogs younger than 6 months of age.

• Dosing needs to be carefully measured for cats, as these preparations are generally formulated for larger animals.

Ivermectin dosing for pets:

• Dogs: 0.0027 mg per pound (0.006 mg/kg) once monthly for heartworm prevention

• Cats: 0.0109 mg per pound (0.024 mg/kg) once monthly for heartworm prevention; 0.01% topically once for ear mites

• Of note, there are multiple off-label uses in pets.

How to take ivermectin

When treating worms, an ivermectin dose should be taken on the day(s) recommended on an empty stomach with water. Ivermectin tablets should be taken with food when treating scabies and lice. 

• Take your medicine as directed. Do not take medicine that was not prescribed to you or that was prescribed for veterinary use. 

• This medication often only needs to be administered once. Your healthcare provider can provide additional doses if you need an extra dose. 

• Read and follow the instructions for this medication. Talk with your healthcare professional if you have any questions. 

Ivermectin dosage FAQs

How long does it take ivermectin to work?

The effects of ivermectin work relatively quickly. For treatment of strongyloidiasis and onchocerciasis, ivermectin is typically taken in a fasted state as it is lipophilic (“fat-loving”), demonstrating a 2.5-fold increase in bioavailability when taken with a fatty meal. Conversely, for this reason, it is typically taken with food to treat scabies and lice to increase the penetration of the drug into the epidermis. 

How long does ivermectin stay in your system?

The half-life of ivermectin in humans is about 18 hours in adults, and the metabolites continue to be excreted in feces for 12 days. 

What happens if I miss a dose of ivermectin?

Typically, ivermectin is only dosed once. However, it may need to be administered multiple times in severe cases of parasites. Missing one of these doses could result in parasitic resistance to the medication or failure to reduce the parasitic load adequately. 

What interacts with ivermectin?

Generally, ivermectin is an extremely safe and well-tolerated medication. There is some evidence of negative drug interactions when administered with warfarin, as the combination may result in an increased risk of bleeding in some individuals. Getting the medical advice of the healthcare provider is particularly important in this circumstance.

Is it safe to take ivermectin during pregnancy?

Animal studies have shown that ivermectin is teratogenic in very high doses. While there are no adequate and well-controlled trials in pregnant women, the drug's label states that it should not be used during pregnancy. 

Ivermectin is excreted in human breast milk in low concentrations. Treatment in breastfeeding mothers should only be considered when the risk of delaying the treatment of the mother is greater than the risk of harm to the newborn. 

Related resources for ivermectin dosages:

• Ivermectin drug label, NIH DailyMed (2023)

• Parasites - , CDC (2024)

• Head lice - epidemiology and risk factors, CDC (2024)

• Soolantra label, FDA (2014)

• New indications for topical ivermectin 1% cream: a case series study, Advances in Dermatology and Allergology (2019)

• Guidelines on the treatment and management of patients with Covid-19, IDSA (2023)

• Canine HeartGard Plus label, Boehringer Ingelheim (2020)

• Feline HeartGard label, Boehringer Ingelheim (2020)

• Acarrex: Ivermectin topical suspension for cats, FDA Report (2025)