Permethrin Treatment for Scabies and Lice
Scabies Treatment
For scabies, apply permethrin 5% cream to all areas of the body from the neck down and wash off after 8-14 hours; one application is generally curative. 1
Application Details
- Adults and older children: Apply from neck to soles of feet, typically requiring 30 grams for an average adult 1
- Infants and geriatric patients: Include scalp, hairline, neck, temple, and forehead in application, as these areas are commonly infested in this population 2, 1
- Timing: Leave on for 8-14 hours before washing off 2, 1
Special Populations
- Pregnant and lactating women: Permethrin is the preferred treatment due to its safety profile 2, 3, 4
- Infants and young children: Permethrin is recommended; avoid ivermectin in children weighing less than 15 kg due to neurotoxicity risk 4
- Crusted (Norwegian) scabies: Requires combination therapy with 5% permethrin cream plus oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 4
Post-Treatment Expectations
- Persistent pruritus after treatment is common and rarely indicates treatment failure 1
- Pruritus may persist for up to 2 weeks after successful treatment 4
- Retreatment is only indicated if live mites are observed after 14 days 1
Lice Treatment (Pediculosis Pubis)
For pubic lice, apply permethrin 1% creme rinse to affected areas and wash off after 10 minutes. 2
Application Details
- Apply to affected areas only 2
- Leave on for exactly 10 minutes before washing off 2, 3
- Use warm water to minimize absorption through vasodilation 3
Special Populations
- Pregnant and lactating women: Permethrin or pyrethrins with piperonyl butoxide are safe options 2
- Children under 2 years: Permethrin is safe; avoid lindane in this age group 2
Follow-Up
- Evaluate after 1 week if symptoms persist 2
- Retreatment is necessary if live lice are found or eggs are observed at the hair-skin junction 2
Critical Management Considerations
Environmental Decontamination (Both Conditions)
- Bedding and clothing: Machine wash and dry using hot cycle, or dry-clean 2
- Alternative: Remove items from body contact for at least 72 hours 2
- Fumigation of living areas is unnecessary 2
Contact Management
- Scabies: Treat all sexual and close personal or household contacts within the preceding month 2, 3, 4
- Lice: Treat sexual partners within the preceding month 2, 3
Eye Involvement
- Never apply permethrin to the eyes 2, 3
- For eyelash infestations with lice, apply occlusive ophthalmic ointment to eyelid margins twice daily for 10 days 2, 3
Common Pitfalls to Avoid
Lindane Contraindications
- Avoid lindane in persons with extensive dermatitis, pregnant or lactating women, and children under 2 years 2, 4
- Never use lindane after a bath, as this increases absorption and neurotoxicity risk 2
- Seizures and aplastic anemia have been reported with lindane use 2, 4
Treatment Failure Management
- If standard permethrin treatment fails, consider alternative regimens such as ivermectin 3
- For scabies, retreatment after 2 weeks is appropriate if symptoms persist or live mites are observed 4
- For lice, switch to an alternative regimen if no response to initial treatment 2