What is the recommended ivermectin dose (200 µg/kg) for adults and children weighing ≥15 kg, and what alternative treatment is advised for pregnant or lactating patients?

Ivermectin Dosing Recommendations

The standard ivermectin dose is 200 µg/kg (micrograms per kilogram) orally for adults and children weighing ≥15 kg, with dosing repeated based on the specific indication. 1

Dosing by Indication

Scabies

• Standard regimen: 200 µg/kg orally, repeated in 2 weeks 2
• This two-dose regimen is necessary because ivermectin has limited ovicidal activity and may not kill all eggs present at initial treatment 2
• Take with food to increase bioavailability and enhance drug penetration into the epidermis 2

Strongyloidiasis

• Single dose: 200 µg/kg orally 1
• Repeat doses generally not necessary, but follow-up stool examinations should verify eradication 1
• Take on empty stomach with water for this indication 1

Onchocerciasis

• Standard dose: 150 µg/kg orally 1
• Retreatment intervals: as short as 3 months for individual patients, or 12 months in mass distribution campaigns 1

Head Lice

• 200 µg/kg repeated in 10 days has shown effectiveness 3
• Alternative regimen: 400 µg/kg repeated in 7 days demonstrated superior efficacy to 0.5% malathion 3

Helminth Infections (Loeffler's Syndrome, Empirical Treatment)

• 200 µg/kg once daily for 3 days during prepatent period 4
• For empirical treatment of asymptomatic eosinophilia: single dose 200 µg/kg combined with albendazole 400 mg 4

Critical Safety Restrictions

Absolute Contraindications

• Children weighing <15 kg: Ivermectin should NOT be used due to risk of blood-brain barrier penetration and neural toxicity 3, 1
• Loiasis co-infection with high microfilarial loads: Risk of fatal encephalopathy; pretreatment assessment mandatory for patients with exposure to West/Central Africa 1

Special Populations

Pregnancy and Lactation:

• Pregnant women: Use permethrin or pyrethrins with piperonyl butoxide instead 2
• Ivermectin is classified as "human data suggest low risk" but safer alternatives exist 2
• Lactating women: Ivermectin is excreted in breast milk; treatment should only occur when benefit to mother outweighs risk to newborn 1

Immunocompromised Patients:

• May require repeated courses at 2-week intervals 1
• Suppressive therapy (once monthly) may be necessary for extra-intestinal strongyloidiasis 1

Severe Liver Disease:

• Safety of multiple doses unknown; use with caution 2

Renal Impairment:

• No dosing adjustments required 2

Practical Dosing Table (from FDA Label)

For 200 µg/kg dosing 1:

• 15-24 kg: 1 tablet (3 mg)
• 25-35 kg: 2 tablets (6 mg)
• 36-50 kg: 3 tablets (9 mg)
• 51-65 kg: 4 tablets (12 mg)
• 66-79 kg: 5 tablets (15 mg)
• ≥80 kg: Calculate 200 µg/kg

Key Clinical Pearls

• Food interaction varies by indication: Take with food for scabies (increases bioavailability), but on empty stomach for strongyloidiasis 2, 1
• Two-dose regimens are standard for most parasitic infections due to limited ovicidal activity 2, 5
• Recent research suggests children aged 2-5 years may require 300 µg/kg and those 6-12 years may need 250 µg/kg to achieve equivalent exposure to adults, though this is not yet standard practice 6
• No FDA approval for head lice treatment, though widely used off-label 3
• Adverse events are generally rare and mild; no withdrawals due to adverse events occurred in comparative trials with permethrin 5