Ivermectin is a broad-spectrum anti-parasitic agent belonging to the avermectin class. It is a semi-synthetic derivative of avermectin B1. In the Indian context, it is a critical medication for mass drug administration (MDA) programs targeting lymphatic filariasis and for treating strongyloidiasis and onchocerciasis (river blindness). It acts by binding to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing paralysis and death of the parasite.
Adult: Typically 150-200 mcg/kg as a single oral dose. For a 12mg tablet: ~1 tablet for a 60-80 kg individual. Specific regimens: Strongyloidiasis: 200 mcg/kg single dose. Onchocerciasis: 150 mcg/kg single dose, repeated every 6-12 months. Scabies: 200 mcg/kg single dose, may be repeated in 1-2 weeks.
Note: Administer orally with a full glass of water on an empty stomach (1 hour before or 2 hours after food) for optimal absorption. Tablets can be crushed if necessary. For filariasis MDA, it is often administered directly under observation.
Ivermectin binds with high affinity to glutamate-gated chloride ion channels (GluCl) found in nerve and muscle cells of invertebrates. This binding increases the permeability of the cell membrane to chloride ions, leading to hyperpolarization of the nerve or muscle cell. The hyperpolarization results in paralysis and eventual death of the parasite. Mammalian ligand-gated chloride channels are not affected by ivermectin at therapeutic doses, providing its selective toxicity.
Pregnancy: Category C: Animal studies show teratogenicity. Use only if potential benefit justifies potential risk to the fetus. Avoid in first trimester unless absolutely necessary. Used in MDA programs for lymphatic filariasis in pregnancy after first trimester.
Driving: May cause dizziness or drowsiness. Patients should be cautioned about operating machinery or driving until their response is known.
| Warfarin | Ivermectin may potentiate anticoagulant effect; monitor INR. | Moderate |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Clarithromycin, Ritonavir) | May increase ivermectin plasma levels, increasing risk of toxicity. | Major |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin, St. John's Wort) | May decrease ivermectin plasma levels, reducing efficacy. | Moderate |
| Benzodiazepines (e.g., Diazepam) | Potential additive CNS depressant effects. | Moderate |
| Valproic Acid | May increase ivermectin concentration; mechanism unclear. | Moderate |
| Other P-glycoprotein substrates/inhibitors | Potential for altered distribution. | Moderate |
Same composition (Ivermectin (12mg)), different brands: