Ivermectin

1. Introduction

Ivermectin is an antiparasitic medication widely used to treat a variety of parasitic infections in humans. It works by binding to specific ion channels in parasites, causing paralysis and death. Ivermectin is effective against several nematodes, ectoparasites, and some off-label viral infections.

2. Indications

  • Approved Indications:
    • Onchocerciasis (river blindness).
    • Strongyloidiasis.
    • Scabies (moderate to severe or crusted).
    • Pediculosis (lice infestation).
    • Other filarial infections (e.g., lymphatic filariasis as part of combination therapy).
  • Off-Label Uses:
    • Rosacea (papulopustular type).
    • Demodicosis.

3. Dosage

  • Adults:
    • Onchocerciasis: 150 mcg/kg orally as a single dose; repeat every 6–12 months as needed.
    • Strongyloidiasis: 200 mcg/kg orally once daily for 1–2 days.
    • Scabies: 200 mcg/kg orally as a single dose; repeat in 7–14 days if needed.
    • Pediculosis: 200 mcg/kg orally as a single dose; repeat in 7 days if needed.
  • Children (>15 kg):
    • Same dosing as adults, adjusted for weight.
  • Elderly:
    • Use the same dosing as adults; monitor for adverse effects.

4. Administration

  • Take orally on an empty stomach with water for optimal absorption.
  • Topical formulations (e.g., for rosacea) should be applied to the skin once daily to the affected areas.

5. Forms Available

  • Tablets: 3 mg, 6 mg, 12 mg.
  • Cream: 1% ivermectin for topical use.

6. Side Effects

6.1. Common Side Effects

  • Dizziness.
  • Nausea.
  • Fatigue.
  • Abdominal pain.

6.2. Less Common Side Effects

  • Rash.
  • Itching (pruritus).
  • Diarrhoea.

6.3. Rare but Serious Side Effects

  • Hypersensitivity reactions.
  • Neurological effects (e.g., confusion, seizures).
  • Mazzotti reaction (fever, rash, and systemic symptoms due to rapid parasite death).

7. Warnings

  • Neurological Disorders: Use cautiously in patients with conditions affecting the blood-brain barrier, as ivermectin may have increased CNS penetration.
  • Severe Parasitic Load: Patients with a heavy parasitic burden (e.g., onchocerciasis) may develop an intense inflammatory response (Mazzotti reaction).

8. Precautions

  • Avoid in children under 15 kg or younger than 5 years unless prescribed by a specialist.
  • Use cautiously in elderly patients and those with liver impairment.
  • Ensure hydration to reduce side effects like dizziness.

9. Interactions

  • Drug-Drug Interactions:
    • Warfarin: May increase anticoagulant effect; monitor INR closely.
    • Benzodiazepines: Increased risk of CNS depression.
    • CYP3A4 inhibitors (e.g., ketoconazole): May increase ivermectin plasma levels.
  • Drug-Food Interactions:
    • Take on an empty stomach to enhance absorption.

10. Monitoring Parameters

  • Symptom resolution (e.g., relief from itching, elimination of parasites).
  • Liver function tests in prolonged therapy.
  • Signs of allergic or inflammatory reactions during treatment.

11. Use in Children

  • Safe for use in children >15 kg. Avoid in children weighing <15 kg due to insufficient safety data.

12. Use in Pregnancy

  • Category C: Use only if the potential benefits outweigh the risks. Avoid use in the first trimester.

13. Use in Elderly

  • Safe with standard dosing, but monitor for side effects, particularly CNS-related symptoms.

14. Use in Kidney Disease

  • No dose adjustment required, but caution is advised in severe renal impairment due to limited data.

15. Use in Liver Disease

  • Use cautiously in hepatic impairment as ivermectin is metabolised in the liver.

16. Patient Counselling Points

  • Take ivermectin on an empty stomach with a full glass of water for best absorption.
  • Report any severe symptoms, such as fever, rash, or confusion, to your doctor immediately.
  • Follow up with your healthcare provider if symptoms do not improve or worsen after treatment.
  • For scabies or lice, ensure proper environmental decontamination (e.g., washing bedding, clothes).
  • Adhere to prescribed dosing intervals for complete parasite elimination.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
StromectolMerck & Co.$30–50 (4 tablets, 3 mg each)
Soolantra (cream)Galderma$150–200 (30 g, 1%)
Generic IvermectinVarious manufacturers$10–20 (10 tablets, 3 mg each)

18. FAQs (15 Questions)

  1. What is ivermectin used for?
    Ivermectin is used to treat parasitic infections such as scabies, lice, onchocerciasis, and strongyloidiasis.
  2. How does ivermectin work?
    It binds to parasite-specific ion channels, causing paralysis and death of the parasite.
  3. How long does ivermectin take to work?
    Symptom relief begins within 1–2 days, but full treatment may require repeated doses depending on the condition.
  4. Can ivermectin cause side effects?
    Yes, common side effects include dizziness, nausea, and fatigue.
  5. Is ivermectin safe during pregnancy?
    Use during pregnancy is not recommended unless the potential benefit outweighs the risk. Avoid during the first trimester.
  6. Can ivermectin be used for children?
    Yes, it is safe for children weighing >15 kg. It is not recommended for children under 15 kg.
  7. What is the recommended dose of ivermectin for scabies?
    A single dose of 200 mcg/kg, repeated after 7–14 days if needed.
  8. Can ivermectin be taken with food?
    It is best taken on an empty stomach for optimal absorption.
  9. Can ivermectin treat viral infections?
    Ivermectin is not officially approved for treating viral infections. Consult your doctor for appropriate use.
  10. What is a Mazzotti reaction?
    It is an inflammatory response to rapid parasite death, presenting with fever, rash, and swollen lymph nodes.
  11. How should ivermectin cream be used?
    Apply a thin layer of ivermectin cream once daily to the affected skin, avoiding the eyes and mouth.
  12. Can I take ivermectin with other medications?
    Consult your doctor, as ivermectin interacts with medications like warfarin and CYP3A4 inhibitors.
  13. How should ivermectin be stored?
    Store at room temperature, away from moisture and heat.
  14. What should I do if I miss a dose of ivermectin?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up.
  15. Is ivermectin available over the counter?
    In most countries, ivermectin requires a prescription. Always consult your doctor before use.