Recommended Ivermectin Dosage for Parasitic Infections
For parasitic infections, ivermectin should be dosed at 200 μg/kg as a single oral dose for strongyloidiasis and 150 μg/kg as a single oral dose for onchocerciasis, with specific dosing based on body weight. 1
Dosage Guidelines by Specific Parasitic Infection
Strongyloidiasis
- Dosage: 200 μg/kg as a single oral dose 1
- Administration: Take tablets on an empty stomach with water
- Follow-up: Stool examinations should be performed to verify eradication of infection
- Weight-based dosing:
- 15-24 kg: 1 tablet (3 mg)
- 25-35 kg: 2 tablets (6 mg)
- 36-50 kg: 3 tablets (9 mg)
- 51-65 kg: 4 tablets (12 mg)
- 66-79 kg: 5 tablets (15 mg)
- ≥80 kg: Calculate at 200 μg/kg
Onchocerciasis
- Dosage: 150 μg/kg as a single oral dose 1
- Administration: Take tablets on an empty stomach with water
- Retreatment: In mass distribution campaigns, typically every 12 months; for individual patients, retreatment may be considered at intervals as short as 3 months 1
- Weight-based dosing:
- 15-25 kg: 1 tablet (3 mg)
- 26-44 kg: 2 tablets (6 mg)
- 45-64 kg: 3 tablets (9 mg)
- 65-84 kg: 4 tablets (12 mg)
- ≥85 kg: Calculate at 150 μg/kg
Other Parasitic Infections
Cutaneous Larva Migrans
- Dosage: 200 μg/kg as a single dose 2
- Alternative: Albendazole 400 mg once daily for 3 days
Whipworm (Trichuris trichiura)
- Dosage: 200 μg/kg once daily for 3 days in combination with mebendazole 100 mg twice daily 2
- Note: Combination treatment improves cure rates in heavy infections
Loiasis
- Dosage: 150-200 μg/kg, most often as a single dose 2
- Alternative regimens:
- Important caveat: Microfilarial threshold should be below 8,000 mf/ml for safe treatment 2
Special Considerations
Microfilarial Thresholds for Ivermectin
- Most guidelines recommend maintaining microfilarial threshold below 8,000 mf/ml for ivermectin therapy 2
- Some guidelines suggest safety at levels up to 30,000 mf/ml or mention elevated risk for Mazzotti reaction only above 50,000 mf/ml 2
- Safety warning: Before treating with ivermectin, Loa loa infection must be excluded in people who have traveled to endemic regions to prevent severe adverse reactions 3
Efficacy and Monitoring
- Ivermectin rapidly reduces microfilarial counts but has no known long-lasting effects on adult worms 4
- For onchocerciasis, a single oral dose of 150 μg/kg repeated once a year leads to marked reduction in skin microfilaria counts and ocular involvement 4
- Some evidence suggests 6-monthly administration may provide better antiparasitic effect compared to yearly administration 5
Safety Profile
- Ivermectin causes minimal side effects at recommended doses and appears sufficiently free of severe adverse reactions to be used on a mass scale 4
- Common adverse effects (80.5% of patients) are typically mild (57%), with fewer moderate (14.1%) or severe reactions (9.4%) 6
- Side effects are significantly correlated with pretreatment microfilarial counts 6
- Ivermectin should be taken with food to increase bioavailability 3
Mechanism of Action
- Ivermectin binds to glutamate-activated chloride channels in nerve or muscle cells of nematodes with high affinity 7
- This causes hyperpolarization by increasing chloride ion permeability, resulting in paralysis and death of the parasites 7
Pitfalls and Caveats
- Ivermectin may not be effective against all stages of parasites, particularly adult worms
- Concurrent parasitic infections are common and may influence treatment outcomes
- Severe adverse reactions can occur in patients with high Loa loa microfilarial loads
- Retreatment may be necessary for certain infections or in cases of treatment failure
- Weight-based dosing is critical for proper efficacy and safety
By following these evidence-based dosing guidelines, clinicians can effectively treat various parasitic infections while minimizing adverse effects and optimizing patient outcomes.