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%). In the 1% w/w topical formulation, it is primarily indicated for the treatment of parasitic skin infestations, most notably scabies caused by Sarcoptes scabiei var. hominis, and head lice caused by Pediculus humanus capitis. It acts by binding to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, leading to increased cell permeability to chloride ions, hyperpolarization, paralysis, and death of the parasite. It has negligible systemic absorption when applied topically as directed.
Adult: For Scabies: Apply a thin layer of cream/lotion from the neck down to the soles of the feet. Wash off after 8-14 hours (typically overnight). A single application is often sufficient. For Head Lice: Apply sufficient quantity to dry hair and scalp. Rinse after 10 minutes. May repeat after 7 days if live lice are observed.
Note: 1. Apply to clean, cool, dry skin. 2. Avoid face, eyes, lips, nostrils, and genital mucous membranes unless specifically indicated for scalp (lice). 3. For scabies, pay special attention to folds: between fingers, wrists, elbows, armpits, waist, buttocks, genitalia. 4. Trim fingernails and apply under nails. 5. All household members and close physical contacts should be treated simultaneously to prevent reinfestation. 6. Wash all clothing, bedding, and towels in hot water and dry on high heat.
Ivermectin exerts its antiparasitic effect by selectively and with high affinity binding to glutamate-gated chloride ion channels (GluCls) found in the nerve and muscle cells of invertebrates. This binding increases the permeability of the cell membrane to chloride ions (Cl-), leading to hyperpolarization of the nerve or muscle cell. Hyperpolarization results in the loss of normal function, flaccid paralysis, and eventual death of the parasite. Mammalian GABA-gated chloride channels are not affected by ivermectin at therapeutic doses, accounting for its high therapeutic index in humans.
Pregnancy: US FDA Pregnancy Category C. Animal studies have shown teratogenic effects at high doses. No adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus. Topical application minimizes systemic exposure.
Driving: Topical ivermectin has no effect on the ability to drive or use machines.
| Warfarin and other oral anticoagulants | Theoretically, systemic absorption could potentiate anticoagulant effect by displacing from protein binding. Risk is minimal with topical use. | Moderate (Theoretical) |
| CYP3A4 inhibitors (e.g., Ketoconazole, Erythromycin, Clarithromycin, Ritonavir) | May increase systemic levels of ivermectin if absorbed. Risk is minimal with topical use. | Moderate (Theoretical) |
| CYP3A4 inducers (e.g., Rifampicin, Carbamazepine, Phenytoin, St. John's Wort) | May decrease systemic levels if absorbed. Not clinically relevant for topical use. | Minor |
| Other topical agents (e.g., corticosteroids, retinoids, abrasive cleansers) | May increase skin irritation and permeability. Avoid concurrent application to the same area. | Moderate |