Permethrin Treatment Regimen for Scabies
A second round of permethrin cream treatment for scabies is typically recommended 7-10 days after the initial application, regardless of symptom improvement, to kill newly hatched mites that may have survived the first treatment. 1, 2
Standard Treatment Protocol
- First application: Apply permethrin 5% cream from head to toe (including scalp, hairline, neck, temple, and forehead in infants and geriatric patients)
- Leave on for 8-14 hours before washing off
- Second application: Apply 7-10 days after the first treatment
Evidence-Based Rationale
The FDA label for permethrin states that "ONE APPLICATION IS GENERALLY CURATIVE" 2. However, this contradicts current clinical guidelines which recommend a second application. This discrepancy exists because:
- Permethrin kills adult mites but has limited ovicidal activity
- Scabies mite eggs hatch 3-10 days after being laid
- A second application ensures newly hatched mites are eliminated before they can reproduce
The CDC and other authoritative bodies recommend the two-application approach to break the life cycle of the parasite 1.
Special Considerations
When Additional Treatment May Be Needed
- Retreatment is necessary if:
- Living mites are demonstrable after 14 days
- New lesions appear
- Symptoms persist beyond 2-4 weeks 1
Important Clinical Pearls
- Persistent itching is common: Itching may persist for several weeks after successful treatment and is rarely a sign of treatment failure 1
- Manage itching with: Topical corticosteroids and oral antihistamines
- Environmental decontamination: Machine wash bedding and clothing using hot cycle, or remove from body contact for at least 72 hours 1
- Treat all household contacts: All household members and close contacts should be treated simultaneously, even if asymptomatic 1
Application Technique
- Thoroughly massage into skin from head to soles of feet
- For adults, scabies rarely infests the scalp, but treatment should include hairline, neck, temple, and forehead
- For infants and geriatric patients, include the scalp in treatment
- Approximately 30 grams is sufficient for an average adult 2
Treatment Efficacy
Research shows that permethrin 5% cream has cure rates of 89-95% at 4 weeks after treatment 1. Some studies suggest that two consecutive days of application may be more effective than a single application 3, but the standard recommendation remains two applications separated by 7-10 days.
Remember that proper application technique and treating all household contacts simultaneously are crucial for successful eradication of scabies.