Is ivermectin safe to use for treating parasitic infections?

Ivermectin Safety for Parasitic Infections

Ivermectin is safe and effective for treating specific parasitic infections when used at appropriate FDA-approved doses, with a well-established safety profile spanning over 25 years of clinical use. 1, 2

Approved Indications

Ivermectin is FDA-approved for:

• Intestinal strongyloidiasis (200 mcg/kg as a single oral dose)
• Onchocerciasis (150 mcg/kg as a single oral dose)
• Off-label uses with strong evidence:
  • Crusted (Norwegian) scabies
  • Pediculosis pubis (pubic lice)
  • Scabies (200 mcg/kg orally, repeated in 2 weeks) 3

Safety Profile

• Mechanism of action: Binds selectively to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing paralysis and death of parasites 1
• Metabolism: Primarily by CYP3A4 in the liver with a plasma half-life of approximately 18 hours 1
• Excretion: Almost exclusively in feces over approximately 12 days, with less than 1% excreted in urine 1

Common Adverse Effects

• Mild to moderate reactions are common but typically transient:

  • Edema
  • Rash
  • Headache
  • Ocular complaints 1, 2

• Mazzotti reaction: In onchocerciasis patients, adverse reactions correlate with pretreatment microfilarial counts rather than concurrent intestinal parasitic infections 4

Special Populations and Precautions

Pregnancy

• Category C: Teratogenic in animal studies at doses higher than those used in humans
• Not recommended during pregnancy unless benefits outweigh risks 1

Breastfeeding

• Excreted in human milk in low concentrations
• Treatment should only be undertaken when benefits outweigh risks 1

Pediatrics

• Safety not established in children weighing less than 15 kg 3, 1

Elderly

• Use caution due to potential decreased hepatic, renal, or cardiac function 1

Important Precautions

1. Loa loa co-infection: Patients with onchocerciasis who are also heavily infected with Loa loa may develop serious or fatal encephalopathy following treatment 1

2. Blood-brain barrier: Ivermectin does not readily cross the blood-brain barrier in humans, contributing to its safety profile 1

3. Drug interactions:

   • May increase INR when co-administered with warfarin
   • P-glycoprotein inhibitors may increase neurotoxicity 1, 5

4. Administration: Should be taken on an empty stomach with water for optimal absorption 1

Efficacy for Parasitic Infections

• Strongyloidiasis: 64-100% cure rate following a single 200 mcg/kg dose 1
• Onchocerciasis: 83.2% decrease in skin microfilariae count 3 days post-treatment and 99.5% decrease after 3 months 1
• Scabies: Highly effective, particularly for crusted scabies 3
• Other parasites: Shows activity against Ascaris lumbricoides and some protozoal infections 4, 6, 7

Follow-up Recommendations

• For strongyloidiasis: At least three stool examinations over three months following treatment to ensure eradication 1
• For scabies: Retreatment 2 weeks after initial treatment if symptoms persist or live mites are observed 3
• For onchocerciasis: Marked reduction maintained for up to 12 months after a single dose 1

Ivermectin has maintained an excellent safety record over more than 25 years of clinical use for parasitic infections when used according to FDA-approved guidelines and dosing recommendations.