What are the approved human indications for ivermectin and their recommended dosing schedules?

Approved Human Indications for Ivermectin

Ivermectin is FDA-approved for treating specific parasitic infections in humans, including onchocerciasis, lymphatic filariasis, strongyloidiasis, scabies, and pediculosis, with standard dosing of 200 mcg/kg for most indications. 1, 2

FDA-Approved Parasitic Indications

Intestinal Parasites

• Strongyloidiasis: Single dose of 200 mcg/kg for immunocompetent patients 3
  • Immunocompromised patients require 200 mcg/kg on days 1,2,15, and 16 to prevent hyperinfection syndrome 3
  • Repeated stool examinations are necessary to document clearance 1
  • Multiple treatment courses may be needed in HIV-infected or immunocompromised hosts, with suppressive monthly therapy sometimes required 1

Filarial Infections

• Onchocerciasis (river blindness): 200 mcg/kg monthly for 3 months, combined with doxycycline 200 mg daily for 6 weeks 4

  • Repeat ivermectin every 3-6 months until asymptomatic, then annually for several years as needed 4
  • Treatment does not kill adult parasites, requiring repeated follow-up and retreatment 1
  • Critical warning: Exclude loiasis co-infection before treatment; patients with high Loa loa microfilarial loads (>8000 mf/ml) risk fatal encephalopathy 3, 1

• Lymphatic filariasis: Approved indication with standard 200 mcg/kg dosing 2

Ectoparasites

• Scabies: 200 mcg/kg as single dose, repeated in 2 weeks 3

  • For a 56-kg patient, this equals four 3-mg tablets (12 mg total) per dose 3
  • Mandatory second dose at 14 days due to limited ovicidal activity 3
  • Crusted (Norwegian) scabies requires intensive treatment: 200 mcg/kg on days 1,2,8,9, and 15, plus daily topical permethrin 3
  • All household and sexual contacts within the previous month must be treated simultaneously 3

• Pediculosis pubis (pubic lice): 250 mcg/kg, repeated in 2 weeks 3

• Head lice: 400 mcg/kg on days 1 and 8 (non-FDA approved but recommended by American Academy of Pediatrics) 3

Skin Manifestations

• Cutaneous larva migrans: 200 mcg/kg as single dose 4, 3

• Loeffler's syndrome (empirical treatment): 200 mcg/kg once daily for 3 days 3

Critical Administration Guidelines

Food Requirements

• Take with food to increase bioavailability approximately 2.5-fold and enhance drug penetration into the epidermis for most parasitic infections 3, 2
• Exception: FDA label states "should be taken on an empty stomach with water" 1
  • This discrepancy reflects updated CDC guidance prioritizing enhanced bioavailability for most indications 3

Absolute Contraindications

• Children weighing <15 kg or <10 years old: Risk of neurotoxicity from blood-brain barrier penetration 3, 1

  • Use permethrin 5% cream instead for scabies in this population 3

• Loiasis co-infection with high microfilarial loads: Risk of fatal encephalopathy 3, 1

Special Population Dosing

• Pregnancy: Classified as "human data suggest low risk" but FDA states "should not be used during pregnancy since safety has not been established" 3, 1

  • Teratogenic in animals at doses near maternotoxic levels (cleft palate, clubbed forepaws) 1

• Breastfeeding: Probably compatible; excreted in low concentrations in human milk 3, 1

• Renal impairment: No dose adjustment required 3

• Hepatic impairment: Use with extreme caution in severe liver disease; safety of multiple doses not established 3, 5

• Elderly: Use cautiously due to greater frequency of decreased organ function 1

Common Pitfalls to Avoid

• Forgetting the second dose for scabies: The 2-week repeat is mandatory, not optional 3

• Expecting immediate symptom resolution: Itching may persist up to 2 weeks after successful scabies treatment due to allergic dermatitis; treat with topical corticosteroids and oral antihistamines 3

• Failing to treat contacts: All household and sexual contacts must be treated simultaneously for scabies 3

• Using in young children: Absolute contraindication in children <15 kg or <10 years due to neurotoxicity risk 3

• Inadequate assessment for loiasis: Patients with significant exposure to West or Central Africa require pretreatment assessment and careful post-treatment follow-up 1

• Assuming cure in immunocompromised patients: Strongyloidiasis control is difficult in these patients; cure may not be achievable and suppressive monthly therapy may be needed 1

Non-Approved Uses

COVID-19

• Not recommended: The Infectious Diseases Society of America specifically recommends against ivermectin for COVID-19 due to insufficient evidence of benefit 6, 7
• Cochrane review found very low- to low-certainty evidence, concluding "reliable evidence does not support use outside well-designed randomized trials" 7

Cancer Treatment

• Not supported by guidelines: Standard clinical doses (200 mcg/kg) are significantly lower than concentrations needed for anti-cancer effects observed in vitro 6
• Safety profile at potentially therapeutic anti-cancer doses has not been established 6