Pharm

Ivermectin

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Ivermectin, Mectizan, Stromectol

  • Indications
  1. Scabies (refractory to Permethrin 5%)
  2. Head Lice
  3. Strongyloidiasis
  4. Onchocerciasis
  • Contraindications
  1. Pregnancy first trimester
  2. Weight <15 kg
  • Mechanism
  1. Developed initially as veterinary anti-parasitic agent
  2. Related to macrolide Antibiotics
  3. Decreases Nerve Impulse transmission
    1. Potentiates GABA-gated chloride channels
    2. Results in Helminth paralysis
  • Medications
  1. Ivermectin 3 mg tablet
  2. Dose 200 mcg/kg equivalents
    1. Weight 15 to 24 kg: 3 mg
    2. Weight 25 to 35 kg: 6 mg
    3. Weight 36 to 50 kg: 9 mg
    4. Weight 51 to 65 kg: 12 mg
    5. Weight 66 to 79 kg: 15 mg
  • Dosing
  • FDA Approved for Adult and Child (weight >=15 kg)
  1. General
    1. Take on an empty Stomach with water
  2. Strongyloidiasis
    1. Ivermectin 200 mcg/kg orally for 1 dose
    2. Consider repeat up to monthly doses in Immunocompromised patients (e.g. HIV Infection)
  3. Onchocerciasis
    1. Ivermectin 150 mcg/kg orally for 1 dose, repeated every 3 to 12 months
  • Dosing
  • Off-Label for Adult and Child (weight >=15 kg)
  1. Scabies or Head Lice (not FDA approved)
    1. Ivermectin 200 mcg/kg orally for 1 dose, and repeat dose in 10 days
  2. Crusted Scabies
    1. Ivermectin 200 mcg/kg orally on days 1, 2, 8, 9, 15 (and consider on days 22 and 29 in more severe cases)
    2. Use in combination with full body Permethrin 5% daily for 7 days, then twice daily until resolution
  3. Public Lice
    1. Ivermectin 250 mcg/kg orally, then repeated in 2 weeks
  4. Cutaneous Larva Migrans
    1. Ivermectin 200 mcg/kg orally daily for 1 to 2 days
  5. Roundworm Infections
    1. Ivermectin 150 to 200 mcg/kg orally for 1 dose
  • Pharmacokinetics
  1. Peak Level: 3-6 hours after intake
  2. Half-Life: >12 hours
  3. Metabolized by Cyp 3A4
  4. Crosses blood brain barrier via P-Glycoprotein (ABCB1 Transporter)
  • Adverse Effects
  • Mazzotti Reaction (Immunologic Reaction in Onchocerciasis to Parasite Death)
  1. Nausea
  2. Fever
  3. Headache
  4. Arthralgias
  5. Urticaria
  6. Ophthalmic complications
  1. Background
    1. Toxicity findings typically resolve within 6-8 hours of ingestion
    2. Lower Doses <500 mg in adults and <5mg/kg in children are typically without reaction
    3. High doses, however, may result in life threatening adverse effects (Seizures, coma, death)
      1. In 2021, patients were taking very high doses (>600 mg daily) for COVID-19 (based on little evidence of benefit)
      2. Patients also ingested high risk formulations (topical Ivermectin, veterinary Ivermectin)
      3. Risks have increased in Idaho and Arkansas where it has inexplicably been made OTC as of 2025
    4. Ilicit drug use risk
      1. Has been used to potentiate the "high" related to Benzodiazepines and Barbiturates
  2. Gastrointestinal Findings
    1. Nausea or Vomiting
    2. Abdominal Pain
    3. Diarrhea
  3. Neurologic Findings
    1. Headache
    2. Dizziness
    3. Hallucinations
    4. Confusion
  4. Cardiopulmonary Findings
    1. Orthostatic Hypotension
    2. Tachycardia
    3. Asthma Exacerbation
  5. Skin Findings
    1. Urticaria
    2. Edema
  6. Management
    1. See Unknown Ingestion
    2. Activated Charcoal
      1. Indicated in early presentation of large ingestion
    3. Supportive Management
      1. ABC Management
      2. Benzodiazepines for Seizures
      3. Consider Intravenous Lipid Emulsion
  • Safety
  1. Safe in children >15 kg (33 pounds)
  2. Considered safe in Lactation (after first week of life)
    1. Poorly excreted into Breastmilk
  3. Pregnancy Category X in first trimester
    1. Unknown or Pregnancy Category C in later pregnancy
  1. Studies show efficacy over Lindane for Scabies
    1. Madan (2001) J Dermatol 28:481-4 [PubMed]
  2. Permethrin 5% appears to be more effective for Scabies
    1. Usha (2000) J Am Acad Dermatol 42:236-40 [PubMed]
  • Drug Interactions
  1. Warfarin
    1. Ivermectin may increase INR levels
  2. CYP3A4 Inhibitor
    1. May increase drug levels of CYP3A4 substrates
  3. P-Glycoprotein Inhibitor
    1. May increase drug absorption of certain drugs (e.g. Statins)
  • Resources
  1. Ivermectin Tablet (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=847a1dd7-d65b-4a0e-a67d-d90392059dac
  • References
  1. (2025) Presc Lett 32(7): 42
  2. Hamilton (2020) Tarascon Pocket Pharmacopoeia
  3. Tomaszewski (2021) Crit Dec Emerg Med 35(9): 32
  4. Meinking (1995) N Engl J Med 333:26 [PubMed]
  5. Fawcett (2003) Am Fam Physician 68(6):1089-92 [PubMed]