What is the recommended treatment for scabies and lice infestations using Permethrin?

Permethrin Treatment for Scabies and Lice Infestations

For scabies, permethrin 5% cream should be applied to the entire body from the neck down and washed off after 8-14 hours, while for lice infestations, permethrin 1% creme rinse should be applied to affected areas and washed off after 10 minutes. 1, 2

Scabies Treatment

First-Line Treatment

• Permethrin 5% cream
  • Apply to all areas of the body from neck down
  • Leave on for 8-14 hours before washing off
  • Approximately 30 grams is sufficient for an average adult 2
  • Safe and effective, with less potential for toxicity than alternatives 1

Application Technique

• Thoroughly massage cream into skin from neck down to soles of feet
• Avoid using hair conditioners before application as they can impair permethrin adherence 2
• For severe cases, application may be extended to include the head, neck, face, and ears

Special Populations

• Pregnant and lactating women: Permethrin 5% cream is safe and recommended 1, 2
• Children: Safe for children 2 months and older 3
• HIV-infected patients: Same treatment regimen as HIV-negative individuals 1

Alternative Treatments

• Lindane 1% lotion/cream (applied for 8 hours)
  • Caution: Not recommended for pregnant women, lactating women, children under 2 years, or persons with extensive dermatitis 1
  • Risk of seizures when applied after bathing or in patients with extensive dermatitis
• Sulfur 6% ointment (applied nightly for 3 nights)
• Oral ivermectin (200 μg/kg) for severe or crusted scabies 2

Lice Treatment (Pediculosis)

First-Line Treatment

• Permethrin 1% creme rinse
  • Apply to affected areas
  • Wash off after 10 minutes
  • Safe for pregnant and lactating women 1

Alternative Treatments

• Pyrethrins with piperonyl butoxide (wash off after 10 minutes)
• Lindane 1% shampoo (apply for 4 minutes)
  • Caution: Not recommended for pregnant women, lactating women, or children under 2 years 1

Special Considerations for Lice

• Do not apply treatments to the eyes
• For eyelash pediculosis: Apply occlusive ophthalmic ointment to eyelid margins twice daily for 10 days 1
• Pubic lice infestation should prompt evaluation for other sexually transmitted infections 4, 5

Environmental Measures (For Both Conditions)

Essential Steps

• Decontaminate bedding and clothing by:
  • Machine washing and drying using hot cycles
  • Dry cleaning
  • Removing from body contact for at least 72 hours 1, 2
• Treat all household members and close contacts, even if asymptomatic 2
• Keep fingernails trimmed to reduce injury from scratching 2

Common Pitfalls to Avoid

• Fumigation of living areas is unnecessary 1
• Failure to treat all close contacts can lead to reinfestation
• Neglecting environmental measures can result in treatment failure 2

Follow-Up

Evaluation Timeline

• Evaluate after 1 week if symptoms persist 1
• Pruritus may continue for up to 2-4 weeks after successful treatment 2
• Re-treatment may be necessary if:
  • Live mites/lice are found
  • Eggs are observed at the hair-skin junction
  • Symptoms persist beyond 2 weeks 1, 2

Treatment Failure Considerations

• Consider alternative regimen if initial treatment fails
• Persistent symptoms beyond 2 weeks may indicate:
  • Treatment failure
  • Reinfestation from untreated contacts
  • Cross-reactivity with other household mites
  • Allergic dermatitis 2

Recent research suggests that for scabies, applying permethrin 5% cream for two consecutive days may be more effective than a single application, with success rates of 87.2% versus 61.8% 6, though this approach is not yet incorporated into official guidelines.