What is the recommended dose of ivermectin (antiparasitic medication) for a patient with scabies who weighs 137 pounds?

Ivermectin Dosing for Scabies in a 137-Pound Patient

For a patient weighing 137 pounds (62 kg), administer ivermectin 200 μg/kg orally, which equals approximately 12.4 mg (typically rounded to 12 mg), and repeat this same dose in 2 weeks. 1, 2

Dose Calculation and Administration

• The standard dose is 200 μg/kg (0.2 mg/kg) for uncomplicated scabies 1, 2
• For 137 lbs (62.2 kg): 62.2 kg × 0.2 mg/kg = 12.4 mg per dose 1
• The medication must be taken with food to increase bioavailability and enhance penetration into the epidermis 1, 2
• A second dose at the same strength is mandatory 14 days after the first dose because ivermectin has limited ovicidal activity and may not kill eggs present at initial treatment 1, 2

Key Treatment Considerations

• No dosage adjustments are required for renal impairment, though the safety of multiple doses in severe liver disease is not established 1, 2
• Permethrin 5% cream remains the first-line treatment and is more cost-effective than ivermectin, but oral ivermectin offers convenience advantages 1, 2
• All close contacts, household members, and sexual partners within the preceding month must be treated simultaneously to prevent reinfection 2

Common Pitfalls to Avoid

• Do not skip the second dose at 2 weeks - this is essential due to ivermectin's limited activity against eggs 1, 2
• Do not expect immediate symptom resolution - pruritus and rash may persist for up to 2 weeks after successful treatment due to ongoing immune response 1, 2
• Ensure the patient takes ivermectin with food - fasting administration significantly reduces drug absorption and efficacy 1, 2
• Decontaminate all bedding and clothing by machine washing/drying on hot cycle or removing from body contact for at least 72 hours 1, 2

When to Consider Treatment Failure

• Symptoms persisting beyond 2 weeks after the second dose warrant evaluation for treatment failure, resistance, or reinfection from untreated contacts 2
• If retreatment is needed, consider combination therapy with topical permethrin or evaluate for crusted scabies in immunocompromised patients 1, 2

Special Population Note

While some research suggests higher doses (400 μg/kg) may achieve cure with a single dose 3, the guideline-recommended dose remains 200 μg/kg repeated in 2 weeks for standard scabies treatment 1, 2