What is the next step in treating scabies that has failed permethrin (antiparasitic medication) treatment twice?

Treatment for Scabies After Permethrin Failure

For patients who have failed two treatments with permethrin, oral ivermectin at a dose of 200 μg/kg, taken with food and repeated in 2 weeks, is the recommended next step in treatment. 1

Treatment Algorithm After Permethrin Failure

• Switch to oral ivermectin at 200 μg/kg, which should be taken with food to increase bioavailability and penetration into the epidermis 1
• Administer a second dose of ivermectin after 2 weeks to ensure complete eradication of the mites 1, 2
• Consider combination therapy with both topical permethrin and oral ivermectin in cases of severe or resistant scabies 3

Reasons for Permethrin Treatment Failure

• Inadequate application of the medication (not covering all affected areas) 1
• Failure to treat all close contacts simultaneously 1
• Reinfection from untreated contacts or fomites 1
• Possible development of permethrin tolerance or resistance 3
• Insufficient decontamination of clothing and bedding 2

Important Considerations for Successful Treatment

• Ensure thorough application of any topical treatment from scalp to toes, as contrary to traditional guidance, the scalp and head can be involved in scabies, especially in infants but also in adults 4
• Implement rigorous environmental decontamination measures:
  • Machine wash and dry all clothing and bedding using hot cycles 1
  • Store items that cannot be washed in sealed plastic bags for at least 72 hours 1, 2
  • Vacuum clean furniture and car seats 2
• Examine and treat all household members and close contacts simultaneously to prevent reinfection 1, 5

Alternative Treatment Options

• Crotamiton lotion can be considered as an alternative treatment:

  • Apply thoroughly to the entire body from chin down, with particular attention to skin folds and creases 6
  • A second application should be done 24 hours later 6
  • Change clothing and bed linen the next day 6
  • Take a cleansing bath 48 hours after the last application 6

• Lindane (1%) or sulfur (6%) ointment may be used as alternatives, but lindane should be avoided in:

  • Children under 10 years 1, 5
  • Pregnant or lactating women 1, 5
  • Persons with extensive dermatitis due to risk of neurotoxicity 1, 5

Special Populations

• For immunocompromised patients, closer monitoring is necessary as they are at increased risk for treatment failure 1
• For pregnant or lactating women, permethrin remains the preferred treatment due to limited safety data for ivermectin 5
• For crusted (Norwegian) scabies, use combination therapy with daily topical permethrin for 7 days plus oral ivermectin on days 1,2,8,9, and 15 1, 5

Follow-Up

• Be aware that rash and pruritus may persist for up to 2 weeks after successful treatment 1, 5
• Consider retreatment if symptoms persist beyond 2 weeks or if live mites are observed 1, 5
• Recent research indicates that consistent second-dose administration of ivermectin and avoiding permethrin monotherapy may improve treatment success rates 2