What is the recommended dosage of ivermectin (antiparasitic medication) for treating scabies?

Ivermectin Dosage for Scabies

The recommended dosage of ivermectin for treating scabies is 200 μg/kg orally, repeated in 2 weeks. 1, 2

Standard Dosing Recommendations

• Oral ivermectin at 200 μg/kg body weight is the standard recommended dose for scabies treatment, with a second dose required after 2 weeks to ensure complete eradication 1, 2
• Ivermectin should be taken with food to increase bioavailability and enhance penetration into the epidermis 2
• No dosage adjustments are required for patients with renal impairment 2
• The safety of multiple doses in patients with severe liver disease is not well established, requiring caution in this population 3

Treatment Considerations by Patient Population

• For standard uncomplicated scabies:

  • 200 μg/kg orally, repeated in 2 weeks 1, 2
  • The second dose is crucial as ivermectin may not be effective against all stages in the parasite's life cycle 4, 5

• For crusted (Norwegian) scabies:

  • Combination therapy is recommended: topical 5% permethrin cream applied daily for 7 days, then twice weekly until cure, plus oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 2

• For infants and children:

  • Permethrin 5% cream is the preferred first-line treatment for infants and young children 1, 2
  • While ivermectin has shown safety in infants and children <15 kg at doses around 223 μg/kg, this remains off-label use 6
  • Studies suggest doses >200 μg/kg may be more effective in pediatric populations 6

• For pregnant women:

  • Permethrin is the preferred treatment during pregnancy 1
  • Ivermectin is classified as "human data suggest low risk" in pregnancy 1

Efficacy and Treatment Outcomes

• Single-dose ivermectin (200 μg/kg) provides cure rates of approximately 62.5% at two weeks, increasing to 87.5% at four weeks after a second dose 5
• The efficacy of ivermectin is higher when the dose exceeds 200 μg/kg and when the interval between doses is less than 10 days 6
• A recent study showed 100% efficacy in preventing scabies transmission when used as pre-emptive therapy in asymptomatic contacts, even with a single dose 7

Common Pitfalls and Recommendations

• Failure to administer the second dose: A single dose is often insufficient as ivermectin may not kill all stages of the parasite's life cycle, particularly eggs 4, 5
• Inadequate contact management: All persons who have had sexual, close personal, or household contact with the patient within the preceding month should be treated simultaneously to prevent reinfection 2
• Neglecting environmental decontamination: Bedding and clothing should be decontaminated by machine washing/drying using hot cycles or removed from body contact for at least 72 hours 2
• Misinterpreting persistent symptoms: Rash and pruritus may persist for up to 2 weeks after successful treatment and should not necessarily prompt additional treatment 2
• Inappropriate use in contraindicated populations: Exercise caution when using ivermectin in patients with severe liver disease 3

Treatment Algorithm

1. Confirm diagnosis of scabies through clinical examination and skin scrapings if available
2. Assess patient factors (age, weight, pregnancy status, immune status)
3. Administer appropriate treatment:
   • Standard cases: Ivermectin 200 μg/kg orally with food
   • Repeat dose after 2 weeks (essential step)
   • For crusted scabies: Follow combination therapy protocol
4. Treat all close contacts simultaneously
5. Decontaminate environment (bedding, clothing)
6. Follow up after 4 weeks to confirm cure