Is ivermectin helpful for humans?

Ivermectin Use in Humans: Evidence-Based Assessment

Ivermectin is only FDA-approved for specific parasitic infections in humans (onchocerciasis and strongyloidiasis) and has no proven therapeutic utility for other conditions, including COVID-19. 1, 2

FDA-Approved Uses

• Ivermectin is FDA-approved as an anti-parasitic agent specifically for:

  • Onchocerciasis (river blindness) - showing excellent microfilaricidal activity 1, 3
  • Strongyloidiasis (intestinal threadworm infection) - with cure rates of 83-92% in clinical trials 1, 4

• For approved parasitic infections, ivermectin works through a specific mechanism:

  • Binds selectively to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells 1
  • Increases cell membrane permeability to chloride ions, causing paralysis and death of parasites 1, 3
  • Has low affinity for mammalian ligand-gated chloride channels, providing selective toxicity 1

Evidence for Other Parasitic Conditions

• Ivermectin shows efficacy against other filarial parasites:

  • Active against Wuchereria bancrofti, Brugia malayi, Loa loa, and Mansonella ozzardi 3, 5
  • Considered an alternative option for lymphatic filariasis mass treatment programs 5, 6

• Additional parasitic conditions with clinical evidence supporting ivermectin use:

  • Crusted scabies - considered a therapeutic option in clinical guidelines 5
  • Gnathostomiasis - currently considered the better therapeutic option 5
  • Cutaneous larva migrans - excellent efficacy where good alternatives are limited 3

COVID-19 Evidence and Recommendations

• The Infectious Diseases Society of America (IDSA) explicitly recommends against ivermectin use for COVID-19: 2

  • For hospitalized patients: Conditional recommendation against use (very low certainty of evidence) 2
  • For ambulatory persons: Strong recommendation against use (moderate certainty of evidence) 2

• Key limitations of ivermectin for COVID-19 treatment:

  • In vitro activity against SARS-CoV-2 requires concentrations considerably higher than achievable in human plasma and lung tissue 2
  • Clinical trials showed no consistent benefit for COVID-19 treatment 2

Safety Considerations

• When used for approved indications at recommended doses, ivermectin has:

  • Generally good tolerability profile 1, 5
  • Plasma half-life of approximately 18 hours following oral administration 1
  • Metabolism primarily through CYP3A4 in the liver 1
  • Excretion almost exclusively in feces over approximately 12 days 1

• Important safety caveats:

  • Higher doses potentially needed for non-approved uses may cause significant adverse effects 2, 7
  • Special caution needed in patients with high microfilarial loads (Loa loa, onchocerciasis) due to risk of severe encephalopathy 5
  • Does not readily cross the blood-brain barrier in humans at therapeutic doses 1

Clinical Decision Making

• For parasitic infections:

  • Confirm diagnosis through appropriate testing before initiating therapy 1
  • Follow recommended dosing: typically 150-200 mcg/kg for most approved indications 1, 4
  • For strongyloidiasis, conduct at least three follow-up stool examinations over three months to ensure eradication 1

• For non-approved uses (including COVID-19):

  • Avoid off-label use for conditions without strong supporting evidence 2
  • Consider established, evidence-based alternatives for non-parasitic conditions 2

Human ivermectin use should be limited to FDA-approved indications or well-established off-label parasitic applications where clinical evidence supports its efficacy and safety.