Ivermectin Dosing and Usage for Parasitic Infections
Standard Dosing Regimens
For most parasitic infections, ivermectin is dosed at 200 μg/kg orally as a single dose, with repeat dosing at 2 weeks for certain conditions. 1, 2
Specific Parasitic Infections
Scabies:
- 200 μg/kg orally, repeated in 2 weeks 1
- Permethrin 5% cream is preferred as first-line therapy (more effective, safer, and less expensive than ivermectin) 1
- Ivermectin has limited ovicidal activity and cannot prevent recurrences from eggs present at initial treatment, necessitating the second dose at 14 days 1
- Must be taken with food to increase bioavailability and enhance drug penetration into the epidermis 1
Strongyloidiasis:
- Single oral dose of 200 μg/kg 2
- Cure rates of 64-100% achieved with single dosing 2
- Follow-up stool examinations required to verify eradication 2
Onchocerciasis:
- 150 μg/kg orally as a single dose 2
- Retreatment intervals: 12 months in mass distribution campaigns, or as short as 3 months for individual patients 2
- Critical limitation: No activity against adult Onchocerca volvulus parasites (only kills microfilariae) 2
Pediculosis Pubis (Pubic Lice):
- 250 μg/kg orally, repeated in 2 weeks 1
- This is an alternative regimen; permethrin 1% cream rinse is first-line 1
- Limited ovicidal activity requires the second dose at 14 days 1
Empirical Treatment for Eosinophilia in Travelers:
- 200 μg/kg as single dose, combined with albendazole 400 mg 1
- Used for possible prepatent or undetected geohelminth infections 1
- Must exclude Loa loa infection BEFORE treating with ivermectin (critical safety consideration) 1
Administration Guidelines
Fasting vs. Fed State:
- Take with food for parasitic skin infections (scabies, lice) to maximize bioavailability and epidermal penetration 1
- For strongyloidiasis, FDA labeling recommends taking on an empty stomach with water 2
- High-fat meals increase bioavailability approximately 2.5-fold 2
Critical Safety Considerations
Contraindications and Cautions:
- Children <15 kg or <10 years old should NOT receive ivermectin 1
- Infants and young children with scabies must be treated with permethrin instead 1
- Patients with severe liver disease: Safety of multiple doses is not established 1, 3
- Renal impairment: No dosage adjustments required 1
Geographic/Co-infection Precautions:
- Mandatory: Exclude Loa loa infection before treating patients who have traveled to endemic regions 1
- Exclude onchocerciasis before treating for other filarial infections 1
- One study showed increased mortality in elderly, debilitated persons receiving ivermectin, though not confirmed in subsequent reports 1
Drug Interactions:
- Primarily metabolized by CYP3A4 2
- P-glycoprotein substrate; genetic polymorphisms or P-glycoprotein inhibitors may increase neurotoxicity risk 4
Pregnancy and Lactation
Ivermectin is classified as "human data suggest low risk" in pregnancy and probably compatible with breastfeeding 1
- For pediculosis pubis and scabies in pregnant/lactating women, permethrin or pyrethrins with piperonyl butoxide are preferred 1
Efficacy Against Multiple Parasites
When treating polyparasitized populations with two doses of ivermectin (200 μg/kg) at 10-day intervals, cure rates are: 5
- 100% for strongyloidiasis, enterobiasis, and cutaneous larva migrans 5
- 99% for ascariasis and pediculosis 5
- 88% for scabies 5
- 84% for trichuriasis 5
- 68% for hookworm disease 5
Common Pitfalls to Avoid
- Do not use single-dose regimens for conditions requiring repeat dosing (scabies, pediculosis) due to limited ovicidal activity 1
- Do not administer immediately after bathing when using topical alternatives like lindane 1
- Do not exceed FDA-approved doses (200 μg/kg for strongyloidiasis; 150 μg/kg for onchocerciasis) 2
- Do not use for COVID-19 treatment - insufficient evidence and pharmacokinetic parameters make therapeutic concentrations unachievable in vivo 4
- Persistent itching after treatment is not treatment failure - may represent inflammatory response rather than active infection 1