What is the recommended treatment protocol for scabies using ivermectin (antiparasitic medication) in adults and children, including dosage, administration, and precautions?

Ivermectin Treatment for Scabies

Primary Recommendation

For uncomplicated scabies in adults and children ≥10 years or ≥15 kg, use oral ivermectin 200 mcg/kg as a single dose, repeated in exactly 2 weeks, taken with food. 1, 2 However, permethrin 5% cream remains the preferred first-line treatment due to superior efficacy, faster symptom relief, and broader safety profile across all age groups. 1, 3

Treatment Protocol by Patient Population

Adults and Children ≥10 Years or ≥15 kg

Standard Dosing:

• Ivermectin 200 mcg/kg orally as a single dose 1, 2
• Mandatory second dose at exactly 14 days due to limited ovicidal activity (does not kill eggs effectively) 1, 2
• For a 56-kg patient, this equals four 3-mg tablets (12 mg total) per dose 2
• Must be taken with food to increase bioavailability and enhance penetration into the epidermis 1, 2

Alternative First-Line Option:

• Permethrin 5% cream applied to all body areas from neck down, washed off after 8-14 hours 1, 3
• Permethrin is more effective (96.9% cure rate vs. 62.4% with single-dose ivermectin), less expensive, and provides faster symptom relief 1, 4, 5

Infants and Children <10 Years or <15 kg

Ivermectin is contraindicated in this population due to potential neurotoxicity from blood-brain barrier penetration 2, 3

• Use permethrin 5% cream instead as the treatment of choice 1, 2
• Apply from neck down, wash off after 8-14 hours 3

Pregnant and Lactating Women

• Ivermectin is classified as "human data suggest low risk" and probably compatible with breastfeeding 2
• Permethrin is particularly recommended for this population as the safer option 3

Crusted (Norwegian) Scabies

Requires aggressive combination therapy due to massive mite burden and high contagiousness: 1, 3

• Oral ivermectin 200 mcg/kg on days 1,2,8,9, and 15 1, 3
• Additional doses on days 22 and 29 may be required for severe cases 1
• Plus topical permethrin 5% cream applied daily for 7 days, then twice weekly until cure 1, 3
• Must take ivermectin with food 3
• Single-application permethrin or oral ivermectin alone will fail 3

Special Population Dosing Adjustments

Renal Impairment:

• No dose adjustments required 1, 2

Hepatic Impairment:

• Use with extreme caution in severe liver disease 2
• Safety of multiple doses unknown in this population 1

Elderly/Debilitated Patients:

• One study showed increased mortality with ivermectin in this population, though not confirmed in subsequent reports 1, 2
• Consider permethrin as safer alternative 6

Critical Management Steps

Simultaneous Contact Treatment:

• All household members, sexual contacts, and close personal contacts within the preceding month must be treated simultaneously, even if asymptomatic 3, 6
• Failure to treat contacts is a leading cause of treatment failure 3

Environmental Decontamination:

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

Follow-Up and Expected Course

Normal Post-Treatment Symptoms:

• Pruritus and rash may persist for up to 2 weeks after successful treatment due to allergic dermatitis 1, 2, 6
• This does not indicate treatment failure 6
• Treat persistent itching with topical corticosteroids and oral antihistamines 2

Reevaluation Timing:

• Assess at 2 weeks post-treatment if symptoms persist 3, 6
• Retreatment should only be considered if:
  • Live mites are observed on microscopy 3, 6
  • Symptoms persist beyond 2 weeks 1, 3

Treatment Failure Causes:

• Forgetting the mandatory second dose at 2 weeks 2
• Resistance to medication 1
• Faulty application of topical treatments 1
• Reinfection from untreated contacts 3
• Inadequate environmental decontamination 6

Comparative Efficacy Data

Research evidence shows permethrin superiority over single-dose ivermectin:

• Two applications of permethrin: 92.5-96.9% cure rate at 2 weeks 4, 5
• Single-dose ivermectin: 62.4-85.9% cure rate at 2 weeks 4, 5
• Two-dose ivermectin: 89.7-92.8% cure rate at 4 weeks 7, 5
• Permethrin provides faster symptom relief 7, 4, 5

Critical Pitfalls to Avoid

• Never skip the second ivermectin dose at 2 weeks - this is mandatory due to poor ovicidal activity 1, 2
• Never use ivermectin in children <10 years or <15 kg - risk of neurotoxicity 2, 3
• Never administer ivermectin without food - bioavailability is significantly reduced 1, 2
• Never use lindane - risk of seizures, aplastic anemia, and neurotoxicity, especially after bathing or in children <10 years 1, 3, 6
• Never treat the patient alone - simultaneous treatment of all contacts is essential 3, 6
• Never expect immediate symptom resolution - itching may persist 2 weeks after successful treatment 1, 2, 6