What is the recommended dosing for ivermectin (anti-parasitic medication) in the treatment of parasitic infections?

Ivermectin Dosing for Parasitic Infections

Standard Dosing Recommendation

The standard dose of ivermectin for parasitic infections in adults is 200 mcg/kg (0.2 mg/kg) as a single oral dose taken on an empty stomach with water. 1, 2

Indication-Specific Dosing

Strongyloidiasis

• Single dose of 200 mcg/kg orally 1, 2
• Immunocompromised patients require extended dosing: 200 mcg/kg on days 1,2,15, and 16 1
• Take on an empty stomach with water to optimize bioavailability 1, 2
• Follow-up stool examinations are necessary to verify eradication 2

Onchocerciasis

• 150 mcg/kg as a single oral dose 2, 3
• For mass distribution campaigns, repeat dosing at 12-month intervals 2
• Individual patients may be retreated at intervals as short as 3 months 2
• Optimal regimen combines ivermectin 200 mcg/kg monthly for 3 months starting on day one of doxycycline 200 mg daily for 6 weeks 1

Scabies

• 200 mcg/kg orally, repeated in 2 weeks 4, 1
• The second dose is necessary because ivermectin has limited ovicidal activity and may not prevent recurrences from eggs present at initial treatment 4
• Ivermectin should be taken with food for scabies treatment to increase bioavailability and epidermal penetration 4
• Permethrin 5% cream is preferred for infants and children under 10 years 4, 1

Pediculosis (Lice)

• Single dose of 200 or 400 mcg/kg orally for lice resistant to topical agents 4
• Second dose given after 9-10 days 4
• Only use in infants weighing over 15 kg 4

Loiasis

• 150-200 mcg/kg as single dose or repeated at monthly, quarterly, or biannual intervals depending on microfilarial load 1
• Critical safety warning: Always exclude co-existing onchocerciasis before treating loiasis, and exclude loiasis before treating lymphatic filariasis or onchocerciasis 1
• Severe adverse events including encephalitis can occur in hypermicrofilaremic patients (>8,000 mf/mL) with loiasis 1, 5

Lymphatic Filariasis

• 200 mcg/kg combined with doxycycline 200 mg daily for 6 weeks for optimal adult worm killing 1

Critical Administration Guidelines

Timing and Food Interactions

• Take on an empty stomach with water for strongyloidiasis and onchocerciasis 1, 2
• Take with food for scabies to increase bioavailability and epidermal penetration 4

Dosing by Body Weight (from FDA Label)

For strongyloidiasis (200 mcg/kg): 2

• 15-24 kg: 1 tablet (3 mg)
• 25-35 kg: 2 tablets
• 36-50 kg: 3 tablets
• 51-65 kg: 4 tablets
• 66-79 kg: 5 tablets
• ≥80 kg: 200 mcg/kg

For onchocerciasis (150 mcg/kg): 2

• 15-25 kg: 1 tablet (3 mg)
• 26-44 kg: 2 tablets
• 45-64 kg: 3 tablets
• 65-84 kg: 4 tablets
• ≥85 kg: 150 mcg/kg

Special Populations

Renal Impairment

• No dose adjustments required 1

Hepatic Impairment

• Safety of multiple doses in patients with severe liver disease is not established 1

Pregnancy and Lactation

• Classified as "human data suggest low risk" in pregnancy 4, 1
• Probably compatible with breastfeeding 4, 1
• Permethrin or pyrethrins with piperonyl butoxide are preferred alternatives for pregnant and lactating women 4

Pediatric Considerations

• Children under 10 years should not receive ivermectin for scabies; permethrin cream is preferred 1
• Infants and young children should be treated with permethrin for scabies 4

Critical Safety Warnings

Mortality Risk

• One study demonstrated increased mortality among elderly, debilitated persons who received ivermectin, though this has not been confirmed in subsequent reports 1
• Exercise particular caution in frail elderly patients 1

Geographic Exposure Considerations

• Always exclude Loa loa infection before treating with ivermectin in anyone who has traveled to endemic regions 1
• Risk of severe adverse events including encephalitis in hypermicrofilaremic patients (>8,000 mf/mL) with loiasis 1, 5

Side Effects

• Side effects are significantly correlated with pretreatment microfilarial counts 6
• Most patients (80.5%) report adverse effects: 57% mild, 14.1% moderate, and 9.4% severe reactions 6
• Generally well tolerated with no indication of CNS toxicity at doses up to 10 times the highest FDA-approved dose 7

Empirical Treatment Strategy

For travelers with eosinophilia and negative stool studies, consider empirical treatment with albendazole 400 mg plus ivermectin 200 mcg/kg as a single dose to cover prepatent or undetected geohelminth infections 1