What are the medical uses for ivermectin?

Medical Uses of Ivermectin

Ivermectin is FDA-approved only for the treatment of strongyloidiasis and onchocerciasis (river blindness), with no proven efficacy for COVID-19 or other viral infections despite its in vitro activity. 1, 2, 3

FDA-Approved Indications

Parasitic Infections

• Strongyloidiasis: Single oral dose of 200 mcg/kg for intestinal strongyloidiasis 3

  • Efficacy measured by absence of larvae in follow-up stool examinations
  • At least three stool examinations should be conducted over three months following treatment to ensure eradication

• Onchocerciasis (River Blindness): Single oral dose of 150 mcg/kg given annually 3, 4

  • Causes dramatic reduction in skin microfilariae counts (83.2% decrease after 3 days, 99.5% after 3 months)
  • Reduction >90% maintained for up to 12 months after a single dose

Off-Label Uses with Clinical Evidence

Other Parasitic Infections

• Lymphatic filariasis: Effective against microfilariae of Wuchereria bancrofti and Brugia malayi 5, 6

  • Used in mass treatment programs though not officially FDA-approved for this indication

• Scabies: Particularly effective for crusted (Norwegian) scabies 5

  • Considered a therapeutic option with strong clinical evidence

• Pediculosis (lice infestations): Effective against head lice 7, 8

• Other nematode infections: Shows activity against:

  • Ascaris lumbricoides (roundworm)
  • Trichuris trichiura (whipworm)
  • Enterobius vermicularis (pinworm)
  • Partial efficacy against hookworms 6

• Gnathostomiasis: Considered an effective therapeutic option 5

Pharmacology and Mechanism of Action

• Mechanism: Binds selectively to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells 3

  • Increases cell membrane permeability to chloride ions
  • Results in hyperpolarization, paralysis, and death of parasites
  • May also interact with GABA-gated chloride channels

• Pharmacokinetics: 3

  • Metabolized in the liver primarily by CYP3A4
  • Plasma half-life approximately 18 hours following oral administration
  • Excreted almost exclusively in feces over approximately 12 days
  • Bioavailability increases 2.5-fold when taken with high-fat meals

Important Cautions and Contraindications

• COVID-19: Both the Infectious Diseases Society of America and American Heart Association strongly recommend against using ivermectin for COVID-19 treatment 1, 2

  • Multiple RCTs have failed to demonstrate meaningful clinical benefit
  • No proven effect on mortality or need for mechanical ventilation

• Cancer: Not recommended for cancer treatment due to insufficient clinical evidence 2

  • Research remains primarily preclinical
  • May divert patients from proven cancer therapies

• Safety concerns: 2, 3

  • Common adverse effects include edema, rash, headache, and ocular complaints
  • May interact with P-glycoprotein inhibitors, increasing neurotoxicity risk
  • Severe systemic postural hypotension can occur (rare)
  • Risk of severe encephalopathy when treating patients with high microfilarial loads (especially with Loa loa)

Emerging Resistance Concerns

• Intensive use has led to emergence of resistance in some parasites 7
• First documented cases of resistance have been reported in treatment of scabies 5

Ivermectin remains a critical medication for treating several parasitic diseases affecting millions worldwide, but its use should be limited to approved indications or off-label applications with substantial clinical evidence supporting efficacy and safety.