What are the potential side effects of Ivermectin (antiparasitic medication)?

Ivermectin Side Effects

Ivermectin commonly causes side effects including dizziness, nausea, headache, and gastrointestinal symptoms, with more serious neurological complications possible at higher doses or in certain populations. 1

Common Side Effects

Ivermectin's side effects can range from mild to severe, depending on dosage, formulation, and individual factors:

Mild to Moderate Side Effects

• Gastrointestinal effects: Nausea, vomiting, diarrhea, abdominal pain 1, 2
• Neurological effects: Dizziness, headache, drowsiness 1, 2
• Skin reactions: Rash, pruritus (itching), urticaria 1
• General symptoms: Fever, fatigue, asthenia (weakness) 1, 2

Severe Side Effects (Less Common)

• Neurological complications: Ataxia (loss of coordination), seizures, confusion, encephalopathy 2
• Allergic reactions: Edema, severe skin reactions 2
• Ocular effects: Red eye, conjunctival hemorrhage 2
• Laboratory abnormalities: Elevated liver enzymes, leukopenia 1

Special Considerations and Risk Factors

Loa loa Co-infection

Patients with concurrent Loa loa infection may develop potentially fatal encephalopathy when treated with ivermectin 1, 2. Pre-treatment assessment for loiasis is essential for individuals from West or Central African endemic areas.

Drug Interactions

• P-glycoprotein inhibitors: Azithromycin can significantly increase serum ivermectin concentration 1, 3
• Warfarin: Rare reports of increased INR when co-administered 2
• High-fat foods: Increase bioavailability by 2.5 times 1
• Alcohol: May worsen side effects 1

Dosing and Toxicity Risks

Toxicity risk increases with:

• Higher than recommended doses 4
• Use of veterinary formulations 4
• Prolonged treatment courses 4
• Genetic polymorphisms affecting P-glycoprotein 3

Population-Specific Considerations

Pregnancy

• Ivermectin should generally be avoided during pregnancy, especially in the first trimester 1
• No teratogenicity has been observed in limited human experience, but animal studies show potential risks 1, 2
• WHO suggests it can be used in second/third trimesters if benefits outweigh risks 1

Breastfeeding

• Very low levels are excreted into breast milk 1
• Generally considered compatible with breastfeeding 1

Elderly Patients

• Treatment should be cautious due to potential decreased hepatic, renal, or cardiac function 2
• Monitor more closely for adverse effects

Monitoring and Precautions

• Liver function: Use with caution in reduced hepatic function 1
• Administration: Take without food but with water for optimal absorption 1
• Driving: Warn patients not to drive due to potential dizziness and drowsiness 1
• QT prolongation: Avoid in patients taking other drugs that cause QT prolongation 1

Overdose Management

In case of accidental overdose or toxicity:

• Supportive therapy including IV fluids and electrolytes
• Respiratory support if necessary
• Pressor agents for significant hypotension
• Gastric lavage and purgatives if ingestion was recent 2

Toxicity Patterns

Recent toxicity cases during the COVID-19 pandemic revealed two distinct patterns:

1. Acute toxicity: Often from veterinary formulations with large single doses, causing rapid onset of neurotoxicity
2. Chronic toxicity: From prolonged use (median 3.8 weeks) of even therapeutic doses, causing milder but persistent symptoms 4

The misuse of ivermectin for COVID-19 prevention or treatment is not recommended due to lack of efficacy and risk of adverse events 3, 5.

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