What is the recommended dosage of ivermectin for treating parasitic infections?

Ivermectin Dosing for Parasitic Infections

The standard dose of ivermectin for most parasitic infections is 200 mcg/kg (0.2 mg/kg) as a single oral dose taken on an empty stomach with water. 1, 2

Standard Dosing by Indication

Intestinal Nematodes

• Strongyloidiasis: 200 mcg/kg as a single oral dose 3, 2

  • Immunocompromised patients require extended dosing: 200 mcg/kg on days 1,2,15, and 16 1
  • Follow-up stool examinations should verify eradication 2
  • Cure rate is 83% with single-dose treatment 4

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

  • Alternative regimen: 200 mcg/kg once daily for 2 days 3

• Hookworm, Ascariasis, Enterobiasis: 200 mcg/kg single dose 5

  • Note: Albendazole is superior for hookworm (98% cure rate vs ivermectin) and should be preferred 4

Filarial Infections

• Onchocerciasis: 150-200 mcg/kg as a single oral dose 3, 2, 6

  • Initial treatment: 200 mcg/kg monthly for 3 months starting on day one of doxycycline 200 mg daily for 6 weeks 3
  • Maintenance: Repeat every 3-6 months until asymptomatic, then annually for several years 3
  • FDA-approved dosing is 150 mcg/kg, with retreatment intervals as short as 3 months or up to 12 months in mass campaigns 2

• Lymphatic filariasis: 200 mcg/kg single dose 7

  • Preferred when microfilarial load is <8,000 mf/mL 4
  • Combine with doxycycline 200 mg daily for 6 weeks for optimal adult worm killing 3

• Loiasis: 150-200 mcg/kg, with dosing frequency (single, monthly, quarterly, or biannual) dependent on microfilarial load 1

Ectoparasites

• Scabies: 200 mcg/kg orally, repeated in 2 weeks 1, 8

  • Cure rate of 88-100% with two-dose regimen 8, 5
  • Do not use in children under 10 years; permethrin cream is preferred 1

• Pediculosis: 200 mcg/kg with two doses 10 days apart achieves 99% cure rate 5

Critical Administration Requirements

Timing and Food Interactions

• Must be taken on an empty stomach with water to optimize bioavailability 1, 2
• This is a non-negotiable requirement for proper absorption 1

Weight-Based Tablet Dosing

For strongyloidiasis (200 mcg/kg) using 3-mg tablets 2:

• 15-24 kg: 1 tablet
• 25-35 kg: 2 tablets
• 36-50 kg: 3 tablets
• 51-65 kg: 4 tablets
• 66-79 kg: 5 tablets
• ≥80 kg: Calculate 200 mcg/kg

Essential Safety Precautions

Pre-Treatment Screening

Always exclude Loa loa infection before treating with ivermectin in anyone who has traveled to endemic regions (Central/West Africa) 3, 1

• Ivermectin can cause severe adverse events including encephalitis in hypermicrofilaremic patients (>8,000 mf/mL) with loiasis 4, 1
• Similarly, exclude onchocerciasis before treating loiasis, and exclude loiasis before treating lymphatic filariasis or onchocerciasis 1

Special Populations

• Pregnancy: Classified as "human data suggest low risk" 1
• Breastfeeding: Probably compatible 1
• Renal impairment: No dose adjustment required 1
• Severe liver disease: Safety of multiple doses not established 1
• Elderly/debilitated patients: One study showed increased mortality, though not confirmed in subsequent reports; use with caution 1

Monitoring

• Albendazole (often used in combination) can cause hepatotoxicity and leukopenia with prolonged use, requiring liver enzyme and blood count monitoring 4
• Ivermectin itself is generally well-tolerated with side effects confined to the first 5 days 7

Empirical Treatment Strategy

For travelers with eosinophilia and negative stool studies, consider empirical treatment with albendazole 400 mg plus ivermectin 200 mcg/kg as a single dose to cover prepatent or undetected geohelminth infections 3, 4

• This combination provides broad-spectrum coverage for most intestinal helminths and some ectoparasites 4, 5
• Exclude Loa loa before administering ivermectin 3
• For children 12-24 months, discuss with an expert before treating 3