What is the appropriate dose of ivermectin for a patient weighing 124 pounds (56 kilograms)?

Ivermectin Dosing for 124-pound Patient

For a patient weighing 124 pounds (56 kg), the appropriate dose of ivermectin is 200 mcg/kg, which equals approximately 11,200 mcg (11.2 mg) total, typically administered as four 3-mg tablets for a single oral dose.

Standard Dosing by Indication

The exact dose depends on the specific parasitic infection being treated:

Scabies Treatment

• Dose: 200 mcg/kg orally, repeated in 2 weeks 1, 2
• For this 56-kg patient: Four 3-mg tablets (12 mg total) as a single dose, then repeat in 14 days 1
• The second dose is essential because ivermectin has limited ovicidal activity and may not prevent recurrences from eggs present at initial treatment 2

Strongyloidiasis Treatment

• Dose: 200 mcg/kg as a single oral dose 3
• For 51-65 kg body weight: Four 3-mg tablets 3
• Follow-up stool examinations should verify eradication 3

Onchocerciasis Treatment

• Dose: 150 mcg/kg as a single oral dose 3
• For 45-64 kg body weight: Three 3-mg tablets 3
• Retreatment intervals can be as short as 3 months for individual patients 3

Other Parasitic Infections

• Cutaneous larva migrans: 200 mcg/kg as a single dose 2
• Pediculosis pubis (pubic lice): 250 mcg/kg, repeated in 2 weeks 2
• Loeffler's syndrome (empirical treatment): 200 mcg/kg once daily for 3 days 1

Critical Administration Guidelines

Food Considerations

• For scabies and most parasitic infections: Take ivermectin WITH FOOD to increase bioavailability and enhance drug penetration into the epidermis 1, 2
• For strongyloidiasis and onchocerciasis: Take on an EMPTY STOMACH with water per FDA labeling 3

This discrepancy exists because different indications have different pharmacokinetic requirements—scabies treatment benefits from enhanced tissue penetration, while intestinal parasites may be better treated with fasting administration 3.

Special Population Considerations

Pregnancy and Lactation:

• Ivermectin is classified as "human data suggest low risk" in pregnancy and is probably compatible with breastfeeding 1, 2
• Very low levels are excreted into breast milk 2
• Permethrin is preferred during pregnancy when treating scabies 1

Renal Impairment:

• No dose adjustments required 1, 2

Hepatic Impairment:

• Use with extreme caution in severe liver disease—the safety of multiple doses is not established 1, 4, 2

Pediatric Patients:

• Safety in children weighing <15 kg has not been determined 1
• Children <10 years should not receive ivermectin for scabies; use permethrin instead 1

Common Pitfalls to Avoid

1. Forgetting the second dose for scabies: The 2-week repeat dose is mandatory due to limited ovicidal activity 1, 2

2. Incorrect food timing: Verify whether the specific indication requires food or fasting administration 1, 3

3. Using in immunocompromised patients without specialist consultation: One study showed increased mortality in elderly, debilitated persons, though not confirmed in subsequent reports 1

4. Inadequate follow-up: Symptoms may persist for up to 2 weeks after successful scabies treatment due to allergic dermatitis 1

5. Treating contacts: For scabies, all household and sexual contacts within the previous month should be treated simultaneously 1