What is the recommended treatment for a patient presenting with scabies?

Scabies Treatment

For uncomplicated scabies, use permethrin 5% cream as first-line treatment, applied from the neck down for 8-14 hours, or oral ivermectin 200 μg/kg repeated in 2 weeks. 1, 2

First-Line Treatment Options

Topical Permethrin 5% Cream

• Apply to all areas of the body from the neck down and wash off after 8-14 hours 1, 2, 3
• Permethrin is effective, safe, and less expensive than ivermectin 1
• Preferred for infants, young children, pregnant women, and lactating women 1, 2, 4
• Safe for children as young as 2 months of age 5
• A single application is generally curative, though a second application 7-10 days later is recommended 1, 6
• Recent evidence suggests applying permethrin once daily for two consecutive days (87.2% cure rate) is more effective than single application (61.8% cure rate) 6

Oral Ivermectin

• Dose: 200 μg/kg body weight, repeated in 2 weeks 1, 2, 3
• Must be taken with food to increase bioavailability and epidermal penetration 1, 2, 3
• The second dose at 2 weeks is essential because ivermectin has limited ovicidal activity 1
• Do not use in children weighing less than 15 kg due to potential neurotoxicity 4
• Not recommended for pregnant or lactating women due to limited safety data 4
• Cure rate of 85.9% at 2 weeks with single dose 7

Alternative Treatments (When First-Line Options Fail or Are Contraindicated)

Lindane 1%

• Apply thinly from neck down and wash off after 8 hours 1
• Should only be used if patient cannot tolerate recommended therapies or if these have failed 1
• Absolute contraindications: children <10 years, pregnant/lactating women, persons with extensive dermatitis 1, 2, 3, 4
• Never apply after bathing (increases absorption and seizure risk) 1, 3
• Risk of neurotoxicity including seizures and aplastic anemia 1
• Resistance reported in some areas of the United States 1

Other Alternatives

• Crotamiton 10%: Apply nightly for 2 consecutive nights, wash off 24 hours after second application 1, 3, 8
• Sulfur 6% ointment: Apply nightly for 3 nights 3

Crusted (Norwegian) Scabies

Requires aggressive combination therapy due to massive mite burden (thousands to millions of mites) 2, 3

• Topical permethrin 5% cream applied daily for 7 days, then twice weekly until cure 2, 3, 4
• PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 2, 3, 4
• Single-application permethrin or single-dose ivermectin will fail 2
• Occurs in immunodeficient, debilitated, or malnourished persons 2
• Far more contagious than typical scabies 2

Environmental and Contact Management

Decontamination

• Machine wash and dry bedding/clothing using hot cycle, or dry clean, or remove from body contact for at least 72 hours 1, 2, 3, 4
• Fumigation of living areas is unnecessary 1, 3
• Keep fingernails closely trimmed to reduce injury from scratching 1, 3

Contact Tracing

• Examine and treat all persons with sexual, close personal, or household contact within the preceding month 1, 2, 3, 4
• All contacts should be treated simultaneously, even if asymptomatic, to prevent reinfection 2, 4
• For institutional outbreaks, treat the entire at-risk population 3

Follow-Up and Expected Course

Normal Post-Treatment Course

• Pruritus and rash may persist for up to 2 weeks after successful treatment 2, 3, 4
• Approximately 75% of patients with persistent pruritus at 2 weeks will have resolution by 4 weeks 5
• This does not indicate treatment failure 2, 3

Retreatment Criteria

• Reevaluate after 1-2 weeks if symptoms persist 1, 2, 4
• Consider retreatment after 2 weeks if symptoms persist beyond expected timeframe or live mites are observed 2, 3, 4
• If no response to first-line treatment, switch to alternative regimen 1

Reasons for Treatment Failure

• Inadequate application of topical treatments 2, 3
• Failure to treat all close contacts simultaneously 2, 3
• Reinfection from untreated contacts or contaminated fomites 2, 3
• Not repeating ivermectin dose after 2 weeks 2, 3
• Medication resistance 3

Critical Treatment Pitfalls to Avoid

• Never use lindane after bathing or showering (increases absorption and seizure risk) 1, 3
• Never use lindane in children <10 years, pregnant/lactating women, or persons with extensive dermatitis 1, 2, 3, 4
• Do not forget the second dose of ivermectin at 2 weeks (limited ovicidal activity requires repeat dosing) 1, 2, 3
• Do not expect immediate symptom resolution (pruritus may persist 2 weeks after successful treatment) 2, 3, 4
• Do not fail to treat all household and close contacts simultaneously 2, 3, 4
• For crusted scabies, never use single-application permethrin alone (will fail due to massive mite burden) 2

Special Populations

Pregnancy and Lactation

• Permethrin 5% cream is the preferred treatment 1, 2, 3, 4
• Pyrethrins with piperonyl butoxide is also acceptable 1
• Avoid lindane (associated with neural tube defects and mental retardation) 1
• Ivermectin has limited human pregnancy data but is classified as "human data suggest low risk" 1

Infants and Young Children

• Permethrin is preferred for infants ≥2 months of age 1, 2, 4, 5
• Ivermectin should not be used in children weighing <15 kg 4
• Never use lindane in children <10 years 1, 2, 3, 4

Immunocompromised Patients

• Higher risk for crusted scabies requiring aggressive combination therapy 2, 3
• Closer monitoring necessary due to increased risk of treatment failure 2