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

Scabies Treatment

Permethrin 5% cream applied to all areas of the body from the neck down and washed off after 8-14 hours is the first-line treatment for uncomplicated scabies, with oral ivermectin (200 μg/kg, repeated in 2 weeks) as an equally effective alternative. 1, 2, 3

First-Line Treatment Options

For most patients with uncomplicated scabies, use permethrin 5% cream as topical first-line therapy:

• Apply to entire body from neck down, including under fingernails, between fingers and toes, and all skin folds 1, 2
• Leave on for 8-14 hours (typically overnight), then wash off thoroughly 1, 4
• One application is generally curative in most cases 5
• Permethrin is safe, effective, and less expensive than ivermectin 1

Oral ivermectin is equally recommended as first-line therapy:

• Dose: 200 μg/kg body weight, repeated in 2 weeks 1, 2
• Must be taken with food to increase bioavailability and epidermal penetration 1, 2
• The second dose at 2 weeks is essential because ivermectin has limited ovicidal activity 1, 2
• Particularly useful for institutional outbreaks, bedridden patients, or when topical application is impractical 6

Special Populations

Pregnant and lactating women:

• Use permethrin 5% cream exclusively 1, 3, 5
• Avoid ivermectin due to limited safety data in pregnancy, though human data suggest low risk 1
• Never use lindane due to association with neural tube defects and accumulation in breast milk 1

Infants and young children:

• Permethrin 5% cream is preferred and safe for infants ≥2 months old 5, 4
• Apply to entire body INCLUDING head, neck, and scalp in infants and young children 5, 6
• Avoid ivermectin in children weighing <15 kg due to potential neurotoxicity 5
• Never use lindane in children <10 years old 1, 3

Immunocompromised patients:

• Higher risk for crusted (Norwegian) scabies requiring more aggressive treatment 3
• Monitor more closely as treatment failure rates are higher 2

Crusted (Norwegian) Scabies

This severe form requires aggressive combination therapy:

• Topical: 5% permethrin cream applied daily for 7 days, then twice weekly until cure 2, 3
• PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 2, 3, 5
• Single-application permethrin or single-dose ivermectin will fail 2
• This population harbors thousands to millions of mites and is far more contagious than typical scabies 2

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

Lindane 1% is now relegated to alternative status due to toxicity concerns:

• Apply thinly from neck down, wash off after 8 hours 1, 3
• Contraindications: children <10 years, pregnant/lactating women, extensive dermatitis, immediately after bathing 1, 3
• Risk of seizures and aplastic anemia, especially with improper use 1
• Resistance reported in some U.S. regions 1

Other alternatives:

• Crotamiton 10% applied nightly for 2 consecutive nights, washed off 24 hours after second application 1, 7
• Sulfur 6% ointment applied nightly for 3 nights 3
• Benzyl benzoate 25% (87% cure rate but causes burning sensation in 43% of patients) 3

Critical Management Steps Beyond Medication

Treat all close contacts simultaneously:

• Examine and treat all persons with sexual, close personal, or household contact within the preceding month 1, 2, 3
• Treat even if asymptomatic to prevent reinfection 5
• This is the most common cause of treatment failure 2, 3

Environmental decontamination:

• Machine wash and dry all bedding, clothing, and towels using hot cycle 1, 2, 3
• Alternatively, dry clean or remove from body contact for at least 72 hours 1, 2
• Fumigation of living areas is unnecessary 1, 2, 3
• Vacuum furniture and carpets 6

Trim fingernails short:

• Mites commonly remain under fingernails 2, 7
• Apply medication under nails using a toothbrush, then discard the brush 7

Follow-Up and Expected Course

Pruritus and rash may persist for up to 2 weeks after successful treatment:

• This is due to ongoing hypersensitivity reaction to dead mites, NOT treatment failure 2, 3, 5
• In clinical trials, approximately 75% of patients with persistent pruritus at 2 weeks had resolution by 4 weeks 4

Consider retreatment only if:

• Symptoms persist beyond 2 weeks 2, 3, 5
• Live mites are observed on examination 1, 2
• New burrows appear 6

Reasons for treatment failure:

• Failure to treat all close contacts simultaneously (most common) 2, 3
• Inadequate application of topical treatment (missing scalp/face in infants, under nails, skin folds) 2, 6
• Not repeating ivermectin dose at 2 weeks 2, 3
• Reinfection from untreated contacts or inadequately decontaminated fomites 2, 3
• True medication resistance (rare but emerging) 1, 6

Critical Pitfalls to Avoid

Application errors with topical permethrin:

• Failing to apply to entire body surface from neck down 2, 6
• Missing scalp and face in infants and young children 5, 6
• Not applying under fingernails 7, 6
• Washing off too soon (must leave on 8-14 hours) 1, 4

Ivermectin errors:

• Not taking with food (reduces bioavailability) 1, 2
• Skipping the second dose at 2 weeks 2, 3
• Using in children <15 kg 5

Lindane misuse:

• Applying immediately after bathing (increases absorption and seizure risk) 1, 3
• Using in contraindicated populations 1, 3

Contact management failures:

• Not treating asymptomatic household contacts 2, 5
• Delaying treatment of contacts (must be simultaneous) 2

Expecting immediate symptom resolution:

• Pruritus commonly persists 1-2 weeks post-treatment 2, 3, 4
• Premature retreatment based on persistent itching alone leads to unnecessary medication exposure 2