What is the maximum dose of ivermectin (antiparasitic medication) for treating scabies?

Maximum Dose of Ivermectin for Scabies Treatment

The maximum recommended dose of ivermectin for treating scabies is 200 μg/kg (micrograms per kilogram) of body weight, which can be repeated after 7-14 days to improve cure rates. 1

Dosing Recommendations

• Standard dose: 200 μg/kg orally as a single dose 1
• Timing of repeat dose:
  • CDC recommends repeating after 14 days 1
  • Some evidence suggests a shorter interval of 7-10 days between doses may improve efficacy 2
• Administration: Should be taken with food to increase bioavailability 1

Efficacy of Ivermectin for Scabies

• Single dose efficacy: 62.5% cure rate at two weeks 3
• After repeat dosing: 87.5% cure rate at four weeks 3
• Higher dosing consideration: A single 400 μg/kg oral dose has shown high efficacy with good tolerance in some studies 4

Special Populations and Considerations

Children and Infants

• Ivermectin should be avoided in children under 15 kg according to standard guidelines 1
• However, emerging evidence supports its safety in infants and young children weighing <15 kg at a dose of approximately 223 μg/kg 5
• For children under 15 kg, permethrin 5% cream remains the first-line treatment 1

Pregnant and Lactating Women

• Permethrin 5% is preferred over oral ivermectin due to established safety data 1

Crusted (Norwegian) Scabies

• More aggressive treatment is required
• Combination therapy with both topical scabicides and oral ivermectin is recommended 2
• May require multiple doses of ivermectin

Treatment Pearls and Pitfalls

Important Clinical Pearls

• Ivermectin is not effective against all life cycle stages of the mite, which explains the need for repeat dosing 2, 3
• Before treating with ivermectin, Loa loa infection must be excluded in people who have traveled to endemic regions to prevent severe adverse reactions 1
• Treatment failure often occurs due to:
  1. Insufficient dosing
  2. Too long interval between doses
  3. Reinfection from untreated contacts

Potential Adverse Effects

• Generally well-tolerated with rare adverse events (4% in one study) 5
• Eczematous eruptions have been reported as a potential adverse effect within 72 hours of administration 4
• Serious adverse reactions are rare but may include Mazzotti reaction in onchocerciasis patients 1

Prevention of Reinfection

• Simultaneous treatment of all household members and close contacts is essential, even if asymptomatic 1
• Decontamination of bedding and clothing by machine washing with hot water or keeping items out of body contact for at least 72 hours 1

Treatment Algorithm

1. First-line: Permethrin 5% cream (especially for pregnant women and children <15 kg)
2. Alternative: Ivermectin 200 μg/kg orally
3. Repeat ivermectin dose after 7-14 days
4. For treatment failures or crusted scabies: Consider combination therapy or higher dosing regimens