Ivermectin is a broad-spectrum anti-parasitic agent belonging to the avermectin class. It is a semi-synthetic derivative of avermectin B1 and is a mixture of two homologues, 22,23-dihydroavermectin B1a (≥80%) and B1b (≤20%). It is a potent positive allosteric modulator of glutamate-gated chloride ion channels found in invertebrate nerve and muscle cells, leading to paralysis and death of parasites. In India, it is a critical drug for mass drug administration (MDA) programs against lymphatic filariasis and for treating strongyloidiasis and onchocerciasis.
Adult: Typically 150-200 mcg/kg as a single oral dose. For a 6mg tablet: Strongyloidiasis: 6mg (one tablet) as a single dose for most adults (approx. 60-80kg). Onchocerciasis: 6mg (one tablet) as a single dose, repeated every 6-12 months until asymptomatic. Filariasis (MDA): 6mg (one tablet) with 400mg Albendazole, annually.
Note: Administer orally with a full glass of water on an empty stomach (1 hour before or 2 hours after food) for optimal and predictable absorption. However, in MDA programs, it is often given without regard to meals for practicality. Tablet can be crushed if necessary for pediatric use. Do not chew.
Ivermectin binds with high affinity to glutamate-gated chloride ion channels (GluCl) which are present in nerve and muscle cells of invertebrates. This binding increases the permeability of the cell membrane to chloride ions, leading to hyperpolarization of the cell. This hyperpolarization results in paralysis of the pharyngeal pumping mechanism in nematodes and paralysis of the somatic muscles in arthropods, ultimately causing death of the parasite.
Pregnancy: Category C: Animal studies have shown teratogenicity at high doses. Use in pregnancy only if the potential benefit justifies the potential risk to the fetus, typically for treatment of strongyloidiasis. In MDA programs for filariasis, pregnancy is a contraindication.
Driving: May cause dizziness or drowsiness. Patients should be cautioned about operating machinery or driving until they know how the drug affects them.
| Warfarin | Ivermectin may potentiate anticoagulant effect; monitor INR closely. | Moderate |
| CYP3A4 Inhibitors (e.g., Clarithromycin, Itraconazole, Ketoconazole, Ritonavir) | May increase ivermectin plasma concentrations, increasing risk of neurotoxicity (dizziness, ataxia). | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin, St. John's Wort) | May decrease ivermectin plasma concentrations, reducing efficacy. | Moderate |
| Benzodiazepines (e.g., Diazepam) | Additive CNS depressant effects; increased risk of drowsiness and dizziness. | Moderate |
| Other CNS Depressants (Alcohol, Barbiturates, Opioids) | Additive CNS depression. | Moderate |
| Valproic Acid | Potential increased risk of neurotoxicity. | Moderate |