What are the standard dosing regimens for oral ivermectin by indication (strongyloidiasis, onchocerciasis, scabies) according to FDA labeling and dosing guides?
Executive summary
Oral ivermectin (Stromectol) is FDA‑approved for two human parasitic infections: intestinal strongyloidiasis and onchocerciasis; the FDA label documents a single 200 micrograms/kg dose for strongyloidiasis and supports single‑dose regimens for onchocerciasis with repeat dosing often used in practice and public‑health programs [1] [2] [3]. Ivermectin is not FDA‑approved for scabies, but clinical dosing guides and practice summaries describe oral regimens—typically 150–250 mcg/kg with a recommended second dose about 7–14 days later—often combined with topical scabicides for ordinary scabies or repeated for crusted scabies [4] [5] [6].
1. Strongyloidiasis: FDA labeling and practical use
The Stromectol (ivermectin tablet) FDA label cites clinical trials in which a single 200 micrograms per kilogram (200 mcg/kg) oral dose cured 64–100% of nondisseminated Strongyloides stercoralis infections, and the label instructs clinicians to monitor clearance with repeated stool exams and to consider repeated courses in immunocompromised patients because optimal regimens in that population are not well defined [1] [2]. Practice references and dosing guides echo the 0.2 mg/kg single dose as the standard, while noting that immunosuppressed patients (including those with HIV) may need repeat or suppressive therapy—monthly or every two weeks in refractory cases—although high‑quality trial data for those strategies are limited [6] [4].
2. Onchocerciasis (river blindness): FDA position and repeat dosing in control programs
The FDA approves ivermectin tablets for onchocerciasis; the drug acts against microfilariae but not adult Onchocerca volvulus worms, so single doses reduce microfilarial load rapidly but do not sterilize adult worms permanently, and additional doses at intervals (commonly 3, 6, or 12 months in clinical practice) are used to control infection and transmission [1] [3]. Dosing commonly used in mass drug administration and programmatic control is about 150 mcg/kg as a single dose, with programmatic frequency determined by local control goals and WHO guidance; public‑health guidelines therefore supplement the FDA label with repeat schedules for long‑term control [7] [8].
3. Scabies: off‑label oral regimens in clinical guides versus FDA approvals
The FDA has not approved oral ivermectin for scabies, and there is no FDA‑specified dosing for that indication; nonetheless, multiple clinical dosing guides and dermatology sources recommend an oral regimen typically in the range of 150–250 mcg/kg as a single dose with a repeat dose about 7–14 days later to kill mites hatching from eggs—practitioners often combine oral ivermectin with topical scabicides and use more frequent or additional doses for crusted scabies [4] [5] [6]. This distinction—FDA approval for certain parasitic diseases but off‑label adoption for scabies—is important for informed prescribing and for patient counseling [9] [4].
4. Safety, caveats, and controversies that shape dosing choices
FDA materials and medicines information emphasize approved indications and warn against unapproved uses (notably repeated public interest around COVID‑19), while clinical references flag the possibility of Mazzotti‑type inflammatory reactions in onchocerciasis, dose adjustments or repeated therapy needs in immunocompromised hosts, and that topical ivermectin formulations (cream/lotion) have separate approvals for skin conditions like rosacea and head lice [10] [1] [6] [9]. Public‑health programs and WHO guidance inform repeat dosing schedules for onchocerciasis and mass drug administration strategies that go beyond single‑patient FDA labeling, underscoring a practical divide between regulatory prescribing information and population‑level control regimens [8] [3].
5. Bottom line for clinicians and programs
For single‑patient prescribing per FDA labeling: use 200 mcg/kg orally once for strongyloidiasis (with stool follow‑up and repeat/suppressive therapy when clinically indicated) and recognize ivermectin’s licensed role in onchocerciasis control where single doses (commonly ~150 mcg/kg in programmatic contexts) are used with repeats as needed; for scabies, follow evidence‑based clinical guidelines—usually a two‑dose oral regimen about 1 week apart in the 150–250 mcg/kg range—acknowledging that this is off‑label and often combined with topical therapy [1] [2] [3] [4] [5]. Where FDA labeling does not specify long‑term or special‑population regimens, rely on disease‑specific guidelines and specialist consultation rather than extrapolating from unapproved uses [8] [10].