What is the recommended oral dose of ivermectin for adults and children over 15 kg with strongyloidiasis, scabies, or onchocerciasis?

Ivermectin Oral Dosing for Strongyloidiasis, Scabies, and Onchocerciasis

For adults and children over 15 kg, ivermectin dosing is indication-specific: 200 mcg/kg as a single dose (repeated in 2 weeks) for strongyloidiasis and scabies, and 150 mcg/kg as a single dose for onchocerciasis. 1

Strongyloidiasis Dosing

• The FDA-approved dose is 200 mcg/kg as a single oral dose, taken on an empty stomach with water 1
• For a practical example: a 56-kg patient receives four 3-mg tablets (12 mg total) 2
• Immunocompetent patients typically require only a single dose, but follow-up stool examinations are mandatory to verify eradication 1, 2
• Immunocompromised patients require an extended regimen of 200 mcg/kg on days 1,2,15, and 16 to prevent hyperinfection syndrome 2

Critical Follow-Up for Strongyloidiasis

• Perform at least three stool examinations over three months post-treatment using concentration techniques (Baermann apparatus), as larvae counts may be very low and recrudescence can occur up to 106 days after treatment 1
• If larvae reappear, retreatment with ivermectin is indicated 1

Scabies Dosing

• The CDC recommends 200 mcg/kg orally, with a mandatory repeat dose in exactly 2 weeks 2, 3, 4
• Take with food to increase bioavailability and enhance drug penetration into the epidermis 2, 3
• For a 56-kg patient, this equals four 3-mg tablets (12 mg total) per dose 2

Special Scabies Populations

• Crusted (Norwegian) scabies requires intensive treatment: ivermectin 200 mcg/kg on days 1,2,8,9, and 15, plus daily topical permethrin 5% cream for 7 days, then twice weekly until cure 2, 3
• Children under 10 years or weighing less than 15 kg have an absolute contraindication to ivermectin due to potential neurotoxicity; use permethrin 5% cream instead 2, 3
• Recent observational data from 170 infants and children weighing 4-14.5 kg showed only mild adverse events (4%) with doses averaging 223 mcg/kg, though this remains off-label 5

Critical Scabies Management Points

• The second dose at 2 weeks is mandatory due to limited ovicidal activity—forgetting this is a common pitfall 2
• All household and sexual contacts within the previous month must be treated simultaneously, even if asymptomatic 3, 4
• Pruritus and rash may persist for up to 2 weeks after successful treatment due to allergic dermatitis; this does not indicate treatment failure 2, 3, 4
• Treat persistent symptoms with topical corticosteroids and oral antihistamines only after confirming no live mites are present 2

Onchocerciasis Dosing

• The FDA-approved dose is 150 mcg/kg as a single oral dose, taken on an empty stomach with water 1
• Weight-based dosing: 15-25 kg receives 1 tablet (3 mg); 26-44 kg receives 2 tablets; 45-64 kg receives 3 tablets; 65-84 kg receives 4 tablets; ≥85 kg receives 150 mcg/kg 1
• Retreatment intervals: 12 months for mass distribution campaigns, but may be as short as 3 months for individual patients 1
• A single 150 mcg/kg dose produces an 83.2% reduction in skin microfilariae at 3 days and 99.5% at 3 months, with >90% reduction maintained for 12 months 1, 6, 7

Onchocerciasis-Specific Considerations

• Ivermectin is microfilaricidal but does not kill adult worms; it temporarily interrupts microfilaria production 6
• There may be a transient increase in anterior chamber microfilariae at day 3, but significant decreases occur by 3 and 6 months 1, 7
• For loiasis co-infection, maintain microfilarial threshold below 8000 mf/ml before using ivermectin to reduce risk of severe adverse events; consider albendazole or apheresis for higher loads 2

Special Population Considerations

• Pregnancy and breastfeeding: The CDC and American Academy of Pediatrics classify ivermectin as "human data suggest low risk" and probably compatible with breastfeeding 2
• Renal impairment: No dose adjustments required 2, 3
• Hepatic impairment: Use with extreme caution in severe liver disease 2
• Avoid in elderly or debilitated patients with loiasis or when using lindane alternatives due to neurotoxicity risk 4

Administration Pitfalls to Avoid

• Food timing varies by indication: take with food for scabies to enhance epidermal penetration, but on an empty stomach for strongyloidiasis and onchocerciasis per FDA labeling 2, 1
• Never use ivermectin in children under 10 years or weighing less than 15 kg for scabies—this is an absolute contraindication 2, 3
• Do not expect immediate symptom resolution; allow up to 2 weeks for post-treatment allergic dermatitis to resolve 2, 3
• Ensure environmental decontamination by machine-washing bedding and clothing in hot water or removing from body contact for at least 72 hours 3, 4