What is the recommended treatment for a patient 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 scabies, with oral ivermectin 200 μg/kg (repeated in 2 weeks) as an equally effective alternative. 1, 2

First-Line Treatment Options

Topical Permethrin 5%

• Apply to entire body from neck down, leave on for 8-14 hours, then wash off 3, 1, 2
• Permethrin is the gold standard due to its superior safety profile, effectiveness, and lower cost compared to ivermectin 3, 2
• Mandatory for infants, young children under 10 years, and pregnant/lactating women 3, 1, 2
• Pruritus may temporarily worsen after application but typically resolves within 2-4 weeks 4

Oral Ivermectin

• Dose: 200 μg/kg body weight, repeated exactly 14 days later 3, 1, 2
• Must be taken with food to increase bioavailability and epidermal penetration 3, 2
• The second dose is essential because ivermectin has limited ovicidal activity and does not kill eggs present at initial treatment 3, 2
• No dosage adjustment needed for renal impairment, but safety uncertain in severe liver disease 3
• Particularly useful for institutional outbreaks, immunocompromised patients, and those unable to apply topical treatments properly 1, 5

Alternative Treatment Options (When First-Line Fails or Unavailable)

Benzyl Benzoate 25%

• Recent high-quality evidence shows 87% cure rate vs. only 27% for permethrin in a 2024 head-to-head trial 6
• Applied daily for 3 consecutive days 6
• Causes burning sensation in 43% of patients but demonstrates excellent efficacy when permethrin fails 1, 6
• Consider as first-line when permethrin resistance is suspected 6

Sulfur 6% Ointment

• Applied nightly for 3 consecutive nights, washing off previous applications before reapplying 1
• A 2022 study showed significantly better efficacy than permethrin (p < 0.001) 7
• Safe option for pregnant women and infants under 2 months 1

Lindane 1% (Last Resort Only)

• Should only be used if patient cannot tolerate recommended therapies or these have failed 3, 1
• Apply thinly from neck down, wash off after 8 hours 3
• Absolute contraindications: children <10 years, pregnant/lactating women, extensive dermatitis, use after bathing 3, 1, 2
• Risk of seizures and aplastic anemia, especially in elderly or debilitated patients 3, 8

Crotamiton 10%

• Apply nightly for 2 consecutive nights, wash off 24 hours after second application 3, 9
• Less effective than other options but may be considered when alternatives unavailable 3

Special Population Considerations

Crusted (Norwegian) Scabies

• Requires aggressive combination therapy due to massive mite burden (thousands to millions of mites) 2
• Regimen: Permethrin 5% cream applied daily for 7 days, then twice weekly until cure PLUS oral ivermectin 200 μg/kg on days 1,2,8,9, and 15 1, 2
• Single-application permethrin or single-dose ivermectin will fail 2
• Occurs in immunocompromised, debilitated, or malnourished patients and is far more contagious than typical scabies 2

Pregnant/Lactating Women

• Permethrin 5% cream is the preferred and safest option 3, 1, 2
• Pyrethrins with piperonyl butoxide is an alternative 3
• Ivermectin classified as "human data suggest low risk" in pregnancy but permethrin still preferred 3
• Never use lindane due to association with neural tube defects and mental retardation 3

Children

• Permethrin 5% is the treatment of choice for all pediatric patients ≥2 months 1, 4
• Lindane absolutely contraindicated in children <10 years due to neurotoxicity risk 3, 1, 2
• Sulfur ointment safe for infants <2 months 1

Immunocompromised Patients

• Higher risk for crusted scabies and treatment failure 1, 2
• Consider combination therapy or more aggressive treatment approach 2
• Closer monitoring necessary 2

Critical Management Steps to Prevent Treatment Failure

Contact Management

• Examine and treat ALL household members, sexual partners, and close personal contacts within the preceding month SIMULTANEOUSLY, even if asymptomatic 3, 1, 2, 8
• This is the most common cause of treatment failure 1, 2, 8
• For institutional outbreaks, treat entire at-risk population 1

Environmental Decontamination

• Machine wash and dry all bedding, clothing, and towels using hot cycle, or dry-clean 3, 1, 2, 8
• Alternatively, remove items from body contact for at least 72 hours 3, 1, 2
• Vacuum furniture and carpets 10
• Fumigation of living areas is unnecessary 3, 1, 2
• Keep fingernails closely trimmed to reduce injury from scratching and mite harboring 1

Application Technique (Critical for Topical Treatments)

• Apply to ALL areas from neck down, including between fingers, under nails, wrists, axillae, abdomen, buttocks, genitalia, and soles of feet 1, 2
• Consider treating face and scalp in infants, elderly, and immunocompromised patients 10
• Use toothbrush to apply under fingernails, then discard brush 9
• Inadequate application is a major cause of treatment failure 1, 2, 10

Follow-Up and Expectations

Normal Post-Treatment Course

• Pruritus and rash may persist for up to 2 weeks after successful treatment and does NOT indicate treatment failure 3, 1, 2, 8
• In clinical trials, 75% of patients with persistent pruritus at 2 weeks had resolution by 4 weeks 4
• This represents an allergic reaction to dead mites and their debris 1, 2

When to Reevaluate

• Evaluate after 1-2 weeks if symptoms persist 3, 1, 8
• Consider retreatment only if live mites are observed or symptoms persist beyond 2 weeks 1, 2, 8

Reasons for Treatment Failure

• Failure to treat all close contacts simultaneously 1, 2, 8
• Inadequate application of topical treatments (missing body areas) 1, 2, 10
• Reinfection from untreated contacts or contaminated fomites 1, 2
• Medication resistance (increasingly reported with permethrin) 7, 6
• Using lindane after bathing (increases absorption and toxicity) 3, 1, 2
• Not repeating ivermectin dose after 2 weeks 1, 2

Treatment Algorithm for Persistent/Recurrent Scabies

1. Verify diagnosis with dermoscopy or skin scraping 6
2. Confirm all contacts were treated simultaneously 8
3. Verify proper application technique and environmental decontamination 8, 10
4. If above confirmed and symptoms persist >2 weeks with live mites, switch to alternative agent:
   • If permethrin failed → try benzyl benzoate 25% or oral ivermectin 1, 6
   • If ivermectin failed → try permethrin or benzyl benzoate 1, 6
   • Consider sulfur ointment as alternative 7
5. Retreat at day 4 based on mite life cycle for more efficient eradication 10

Key Pitfalls to Avoid

• Expecting immediate symptom resolution (may take 2-4 weeks) 1, 2, 8, 4
• Treating patient without treating contacts (guarantees reinfection) 1, 2, 8
• Using lindane in contraindicated populations (children, pregnancy, extensive dermatitis) 3, 1, 2
• Applying lindane after bathing (increases systemic absorption and seizure risk) 3, 1
• Single-dose ivermectin without 2-week repeat (eggs survive and hatch) 3, 1, 2
• Incomplete body coverage with topical agents (missing interdigital spaces, genitalia, under nails) 1, 2, 10
• Assuming permethrin always works (resistance increasingly reported) 7, 6