What is the appropriate ivermectin dosage (200 µg/kg) for a 70‑kg adult and a 20‑kg child, including repeat dosing for immunocompromised or severe cases and the addition of albendazole (400 mg) for hyperinfection?

Ivermectin and Albendazole Dosing Examples

For a 70-kg adult with uncomplicated strongyloidiasis or helminth infection, administer ivermectin 14 mg (200 µg/kg × 70 kg = 14,000 µg = 14 mg) as a single oral dose with albendazole 400 mg; for a 20-kg child, give ivermectin 4 mg (200 µg/kg × 20 kg = 4,000 µg = 4 mg) as a single dose with albendazole 400 mg. 1

Standard Dosing for Uncomplicated Cases

Adults (≥60 kg or 70 kg example):

• Ivermectin: 200 µg/kg as a single dose
  • For 70 kg: 14 mg total dose
• Albendazole: 400 mg as a single dose
• Take both medications with food 1

Children (20 kg example):

• Ivermectin: 200 µg/kg as a single dose
  • For 20 kg: 4 mg total dose
  • Note: Ivermectin should not be used in children weighing <15 kg 2
• Albendazole: 400 mg as a single dose (same as adults for children >24 months) 1
• Administer with food

Modified Dosing for Immunocompromised or Severe Cases

Immunocompromised Patients (Strongyloidiasis):

For both 70-kg adults and 20-kg children, use ivermectin 200 µg/kg on days 1,2,15, and 16 (14 mg per dose for 70 kg; 4 mg per dose for 20 kg), rather than a single dose. 1

This intensive regimen addresses the risk of hyperinfection syndrome in immunosuppressed individuals, which can be fatal if inadequately treated.

Hyperinfection Syndrome:

• Prolonged treatment is required—seek specialist advice immediately 1
• Consider adding albendazole 400 mg twice daily for 21 days in severe cases 1
• Prednisolone 40-60 mg once daily may be needed in severe disease 1
• Monitor closely; intensive care may be necessary 1

Important Clinical Considerations

Repeat Dosing Scenarios:

• Empirical treatment: Consider retreating at 8 weeks for possible prepatent infections 1
• Loeffler's syndrome: Retreat 1 month after resolution of pulmonary symptoms to ensure adult worms are eliminated 1
• Treatment failure: A second dose may be needed if viable nits/parasites persist 3

Critical Safety Points:

Before administering ivermectin:

• Exclude Loa loa infection in patients from endemic regions (Central/West Africa) to prevent severe Mazzotti reactions 1
• Verify weight ≥15 kg for children 2
• Obtain pregnancy test in females of reproductive potential before albendazole 4

Monitoring requirements when using albendazole:

• Check blood counts at baseline and every 2 weeks during therapy 4
• Monitor liver enzymes at baseline and every 2 weeks 4
• Discontinue if clinically significant changes occur 4

Dosing Pitfalls to Avoid:

1. Don't underdose children: Recent evidence suggests children aged 2-5 years may need 300 µg/kg and those 6-12 years may need 250 µg/kg to achieve equivalent exposure to adults, though current guidelines still recommend 200 µg/kg 5

2. Don't use single-dose regimens in immunocompromised patients: These individuals require the multi-day protocol (days 1,2,15,16) 1

3. Don't forget food: Both medications should be taken with meals to optimize absorption 4

4. Don't confuse µg with mg: Ivermectin is dosed in micrograms per kilogram (µg/kg), not milligrams

Practical Calculation Method:

Simple formula: Body weight (kg) × 0.2 = ivermectin dose in mg

• 70 kg × 0.2 = 14 mg
• 20 kg × 0.2 = 4 mg