What is the recommended treatment for an adult patient with scabies?

Scabies Treatment in Adults

Permethrin 5% cream applied from the neck down (or scalp-to-toes in elderly/immunocompromised patients) for 8-14 hours is the first-line treatment for scabies in adults, with oral ivermectin 200 μg/kg (repeated in 2 weeks) as an equally effective alternative. 1, 2

First-Line Treatment Options

Topical Permethrin (Preferred)

• Apply permethrin 5% cream to all body areas from the neck down and wash off after 8-14 hours 1, 2, 3
• For elderly patients (>65 years) and immunocompromised individuals, apply scalp-to-toes including hairline, neck, temple, and forehead 1, 2
• One application is generally curative 3
• Permethrin is more effective, safer, and less expensive than ivermectin for standard scabies 1
• Repeat treatment after 7-10 days if symptoms persist or live mites are observed 1, 2

Oral Ivermectin (Co-First-Line)

• Dose: 200 μg/kg body weight, taken with food, repeated in 2 weeks 1, 2
• Taking with food increases bioavailability and epidermal penetration 1, 2
• The second dose is essential because ivermectin has limited ovicidal activity and does not kill eggs present at initial treatment 1
• Particularly useful for institutional outbreaks, patients unable to apply topical therapy, and as prophylaxis for close contacts 4

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

Lindane 1%

• Apply thinly from neck down, wash off after 8 hours 5, 1
• Contraindicated in children <10 years, pregnant/lactating women, and persons with extensive dermatitis due to neurotoxicity risk 1, 2
• Never use after bathing, as this increases absorption and seizure risk 5, 1
• Resistance reported in some geographic areas 5

Crotamiton 10%

• Apply to entire body from neck down nightly for 2 consecutive nights 5, 6
• Wash off 24 hours after the second application 5, 6
• Less effective than permethrin or ivermectin 5

Sulfur 6% Ointment

• Apply thinly to affected areas nightly for 3 nights, washing off previous applications before reapplying 1
• Safe option for pregnant women when permethrin is unavailable 1

Special Populations

Pregnant and Lactating Women

• Permethrin 5% cream is the preferred treatment 1, 2, 7
• Ivermectin is classified as "human data suggest low risk" in pregnancy and probably compatible with breastfeeding 1
• Avoid lindane completely 5, 1

Crusted (Norwegian) Scabies

• Requires aggressive combination therapy: 1, 2
  • 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
• Single-application permethrin or single-dose ivermectin will fail 2
• Occurs in immunocompromised, debilitated, or malnourished patients with thousands to millions of mites 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, 7
• Fumigation of living areas is unnecessary 5, 1, 2
• Keep fingernails closely trimmed to reduce injury from scratching 1

Contact Treatment

• Examine and treat all persons with sexual, close personal, or household contact within the preceding month 1, 2, 7
• Treat contacts simultaneously to prevent reinfection 1, 2
• For institutional outbreaks, treat the entire at-risk population 1

Follow-Up and Management of Persistent Symptoms

Expected Post-Treatment Course

• Pruritus may persist for up to 2 weeks after successful treatment and is NOT an indication for retreatment 1, 2, 3
• This represents a sensitization reaction rather than active infestation 1

Retreatment Criteria

• Consider retreatment after 2 weeks if: 1, 2
  • Live mites are observed
  • Symptoms persist beyond 2 weeks
  • New lesions develop
• Demonstrable living mites after 14 days indicate retreatment is necessary 3

Reasons for Treatment Failure

• Resistance to medication 1
• Faulty application of topical treatments (incomplete coverage) 1, 2
• Reinfection from untreated contacts or fomites 1, 2
• Not repeating ivermectin dose after 2 weeks 1

Critical Pitfalls to Avoid

• Failure to treat all close contacts simultaneously 1, 2
• Inadequate application of topical treatments (missing skin folds, interdigital spaces) 1, 2
• Using lindane after bathing or in contraindicated populations 5, 1, 2
• Not repeating ivermectin dose after 2 weeks 1
• Retreating based on persistent pruritus alone within 2 weeks 1, 2, 3
• Failing to include scalp/face in elderly or immunocompromised patients 1, 2
• Using topical corticosteroids during active treatment (may allow mites to proliferate) 2