Ivermectin is a proven generic medicinal drug used to treat parasitic infestations such as those caused by intestinal worms (strongyloidiasis of the intestinal tract and onchocerciasis) in animals and humans. Topical forms of ivermectin can also be effective against the rosacea skin condition and certain ectoparasites like head lice and human itch mite.

Ivermectin falls into the category of drugs known as macrocyclic lactone – a complex chemical with robust anti-parasitical action that exhibits high effectiveness in the treatment of worm infestations and excellent tolerability in both humans and animals.

Mechanism of action of Ivermectin

Ivermectin causes the paralysis and death of parasites through selective binding and high affinity for glutamate-gated chloride channels found in the nerve and muscle cells of invertebrates. In the absence of glutamate-gated chloride channels in mammals, ivermectin does not produce any toxic effect on the human central nervous system, in which similar channels are protected by the blood-brain barrier.

The mechanism of action of ivermectin in the treatment of inflammatory skin lesions like rosacea may be associated with both the drug’s significant anti-inflammatory effect that suppresses the production of inflammatory cytokines induced by lipopolysaccharides or its ability to kill Demodex folliculorum mites, which might be a factor causing skin inflammation.

Both brand-name and generic ivermectin are available as oral 3mg tablets. The correct dose of ivermectin is determined with regard to the patient’s specific health problem, age, concomitant diseases, and other essential factors. Below are some general recommendations on the possible ivermectin dosing regimen.

Strongyloidiasis:

  • 15-24 kg: 3mg
  • 25-35 kg: 6mg
  • 36-50 kg: 9mg
  • 51-65 kg: 12mg
  • 66-79 kg: 15mg
  • Over 80 kg: 200mcg/kg

All of the above doses need to be taken orally once. No repeat dose is usually required.

Onchocerciasis:

  • 15-25 kg: 3mg
  • 26-44 kg: 6mg
  • 45-64 kg: 9mg
  • 65-84 kg: 12mg
  • Over 85 kg: 150mcg/kg

All of the above doses need to be taken orally once. A repeat dose might be required in 3 to 12 months after the first dose.

Ascariasis and Larva Migrans:

0.2mg/kg orally once

Filariasis:

0.2mg/kg orally once

Scabies:

0.2mg/kg orally once, with a repeat dose in 14 days. Also, patients might be advised to combine oral medicine with a topical pyrethroid.

Ivermectin tablets are best taken on an empty stomach with a glass of water, usually, 1 hour before breakfast unless otherwise is specified by the prescribing physician. Patients should take only as much of this drug as recommended by the doctor. If they suspect they may have overdosed on ivermectin, patients should seek urgent medical care right away.

Side effects

Ivermectin is generally a favorably tolerated drug, with very few side effects reported. Any adverse reactions that occur after the administration of ivermectin are usually transient. The most common side effects manifesting in less than 5% of patients taking oral ivermectin include:

  • mild fever
  • headache
  • dizziness
  • fatigue
  • irritation, itching, and dryness of skin (when applied topically and by ingestion)
  • eye redness (when applied topically)
  • decreased appetite
  • upset stomach
  • nausea
  • stomach pain
  • bloating
  • constipation
  • joint and muscle pain
  • hypotension

The above reactions are mild to moderate and usually reduce or disappear with continued therapy. They do not necessitate emergency medical intervention. However, if any of these symptoms linger for more than a few days or get more severe, patients are advised to visit their prescribing physician for a consultation.

In rare cases, patients may experience more intensive and dangerous reactions to the ivermectin drug, which manifest through the following symptoms:

  • allergic reaction to ivermectin or any of its excipients
  • accelerated heartbeat
  • painful sensations or swelling of the glands in the neck, armpit, and groin
  • blistering skin
  • chest pain
  • seizures
  • loss of balance
  • labored breathing

In the event of any of the symptoms listed above, patients should stop taking ivermectin immediately and call their doctor or request emergency medical assistance.

Ivermectin for pregnant women/nursing mothers and children: the drug is contraindicated in women during pregnancy or while breastfeeding due to its possible teratogenic and maternotoxic effects. Pediatric use of ivermectin in patients under the age of 5 or weighing less than 15kg is also not recommended due to the limited data on the effectiveness and safety of the drug for this category of patients.

Contraindications of Ivermectin

The medical practitioner prescribing ivermectin should be given the patient’s full medical history, especially if there are any pre-existing skin issues. People with liver or kidney diseases, asthma, seizures, Loa-Loa worm coinfection, sowda (chronic hyperreactive onchodermatitis), and immunocompromised HIV patients or organ recipients should not use ivermectin. It is essential to notify the prescribing physician if patients have hypersensitivity to the central ingredient of ivermectin or any of its excipients.

Drug interactions

Ivermectin can have mild-to-moderate interactions with a wide range of brand-name drugs and OTC generic medications. However, there have been no reports of serious or critical reactions. Some of the drugs ivermectin should be taken cautiously with include:

  • central nervous system depressants (butalbital, phenobarbital)
  • anticonvulsants (valproic acid)
  • benzodiazepines (lorazepam, clonazepam)
  • narcolepsy drugs (sodium oxybate)
  • blood-thinners (warfarin).

Patients on ivermectin should also avoid using alcohol alongside this drug, as this combination can cause increased plasma levels of ivermectin, making the possible side effects more adverse, complex, and prolonged.