What is the recommended treatment for a patient with scabies?

Scabies Treatment

Use permethrin 5% cream as first-line treatment, applied from the neck down (or scalp-to-toes in infants and select cases) for 8-14 hours, with a repeat application after 1-2 weeks if needed. 1, 2

First-Line Treatment Options

Permethrin 5% cream is the preferred topical agent for uncomplicated scabies in most patients, including pregnant women, lactating women, and children over 2 months of age. 1, 2, 3 The CDC and American Academy of Dermatology both endorse this as first-line therapy given its superior safety profile compared to alternatives. 1, 2

Application technique:

• Apply to all areas from neck down (or scalp-to-toes in infants <2 years and immunocompromised patients) 1, 4
• Leave on for 8-14 hours before washing off 1, 2
• Repeat application after 1 week 1
• Apply under fingernails after trimming them short 1

Oral ivermectin 200 μg/kg is an equally effective first-line option, particularly useful for institutional outbreaks, patients who cannot apply topical treatments adequately, or those with multiple household contacts. 1, 2 Take with food to increase bioavailability, and repeat the dose after 2 weeks. 1, 2 Research shows single-dose ivermectin achieves only 62.4% cure rate, but two doses at 2-week intervals increases this to 92.8%, comparable to permethrin's 96.9% cure rate. 5

Special Populations

Pregnant and lactating women: Permethrin 5% cream is the preferred and safest option. 1, 3 The FDA classifies it as Pregnancy Category B with no evidence of fetal harm in animal studies. 6

Children:

• Use permethrin for children ≥2 months of age 6
• Never use lindane in children <10 years due to neurotoxicity risk 1, 2
• Apply permethrin scalp-to-toes in infants and young children, as head involvement is common in this age group 4

Immunocompromised patients: These patients are at high risk for crusted (Norwegian) scabies and require more aggressive treatment with closer monitoring. 1, 2

Crusted (Norwegian) Scabies

Use combination therapy immediately for this highly contagious variant that harbors thousands to millions of mites. 1, 2 Single-agent therapy will fail. 2

Treatment regimen:

• Permethrin 5% cream applied daily for 7 days, then twice weekly until cure 1, 2
• PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 2
• The multiple ivermectin doses address its limited ovicidal activity and the massive mite burden 2

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

Lindane 1%: Apply thinly from neck down, wash off after 8 hours. 1, 2 However, avoid lindane in children <10 years, pregnant/lactating women, persons with extensive dermatitis, and never apply after bathing (increases absorption and seizure risk). 1, 2

Sulfur 6% ointment: Apply nightly for 3 nights, washing off previous applications before reapplying. 1 This is particularly useful when other options are contraindicated.

Crotamiton 10%: Apply nightly for 2 consecutive nights, wash off 24 hours after second application. 1, 7

Benzyl benzoate 25%: Shows 87% cure rate but causes burning sensation in 43% of patients. 1

Critical Management Steps

Treat all close contacts simultaneously within the preceding month, including sexual partners, household members, and close personal contacts. 1, 2 This is the most common cause of treatment failure. 1

Environmental decontamination:

• Machine wash and dry bedding/clothing using hot cycle 1, 2
• Alternatively, dry clean or remove from body contact for ≥72 hours 1, 2
• Fumigation is unnecessary 1, 2

Common Pitfalls to Avoid

• Inadequate application of topical treatments (must cover entire body surface as directed) 1, 2
• Failure to treat all contacts simultaneously leads to reinfection 1, 2
• Not repeating ivermectin dose after 2 weeks results in treatment failure 1, 2
• Using lindane after bathing or in contraindicated populations increases neurotoxicity risk 1, 2
• Expecting immediate symptom resolution - pruritus may persist up to 2 weeks after successful treatment 1, 2, 6

Follow-Up and Treatment Failure

Pruritus and rash may persist for up to 2 weeks after successful mite eradication due to hypersensitivity reaction to dead mites. 1, 2, 6 In clinical trials, approximately 75% of patients with persistent pruritus at 2 weeks had resolution by 4 weeks. 6

Consider retreatment after 2 weeks if:

• Live mites are observed 1, 2
• New lesions appear 1
• Symptoms persist beyond 2 weeks 1, 2

Reasons for treatment failure:

• Resistance to medication 1
• Faulty application technique 1
• Reinfection from untreated contacts or fomites 1, 2
• Unrecognized crusted scabies requiring more aggressive therapy 1