What parasitic infections is ivermectin FDA-approved to treat in humans and what are the recommended dosages?
Executive summary
Ivermectin tablets (human formulations such as Stromectol) are FDA‑approved in the United States to treat two specific parasitic worm infections: intestinal strongyloidiasis (Strongyloides stercoralis) and onchocerciasis (river blindness, Onchocerca volvulus) [1] [2] [3]. The standard approved oral dosing for adults and children ≥15 kg is weight‑based at about 200 micrograms (0.2 mg) per kilogram as a single dose for strongyloidiasis and single doses of roughly 150–200 mcg/kg per treatment cycle for onchocerciasis, with retreatment schedules used in practice [4] [5] [3].
1. What the FDA has explicitly approved — narrow, evidence‑driven indications
The FDA has approved oral ivermectin tablets for two human helminth infections: intestinal strongyloidiasis and onchocerciasis (river blindness). Multiple clinical and regulatory summaries state the tablet formulation indication for these two parasitic worm diseases and note that other uses are “off‑label” or not FDA‑approved [6] [1] [2] [3].
2. Approved dosing in plain numbers: how clinicians dose it
For patients weighing 15 kg or more, prescribing information and major clinical references set dosing based on body weight: approximately 200 micrograms (mcg)/kg (0.2 mg/kg) given as a single oral dose for strongyloidiasis; onchocerciasis is typically managed with single doses in the 150–200 mcg/kg range with retreatment intervals depending on clinical context [4] [5] [3]. Clinical sources provide tabulated mg‑per‑weight conversions for practical prescribing [3] [5].
3. Off‑label but common uses: scabies, lice and topical forms
Dermatology and infectious‑disease sources describe ivermectin’s routine off‑label use for scabies and lice, and note topically formulated ivermectin products have separate approvals (e.g., topical ivermectin cream for rosacea and lotion for head lice) — but oral ivermectin for scabies remains off‑label in many jurisdictions and is used when topical therapy fails or is impractical [6] [1] [7]. Regulatory and clinical summaries emphasize these are not the FDA‑listed oral tablet indications [6] [1].
4. Retreatment, mass administration and dose variation in public‑health practice
Public‑health programs and WHO/NGO mass‑drug administration campaigns use standardized single doses (commonly 150–200 mcg/kg) and repeat dosing schedules for control of onchocerciasis and lymphatic filariasis; retreatment intervals and mass‑administration protocols differ from one‑time curative dosing and are tailored to program goals [5] [8]. Clinical references stress that ivermectin does not reliably kill adult Onchocerca worms, so repeat treatments and monitoring are standard [3] [5].
5. Safety, dosing limits and why veterinary formulations are dangerous
Authors and official advisories repeatedly warn that veterinary ivermectin formulations are different and can be highly toxic if taken by humans; safety data and approved dosages are based on human tablet or topical formulations, not animal products [9] [6] [10]. Sources also note that studies have assessed higher doses in research settings, but routine clinical dosing remains in the 150–200 mcg/kg window for approved indications [11] [8].
6. Where reporting diverges and what is not FDA‑approved
Since 2020 there has been confusion and politicization about ivermectin’s use for COVID‑19; authoritative sources and the FDA explicitly state ivermectin is not approved for prevention or treatment of COVID‑19 [9] [12] [2]. Some research groups and advocacy outlets continue to debate off‑label and investigational uses (e.g., cancer, malaria transmission strategies, or very high‑dose trials), but those are experimental and not FDA approvals [13] [8]. Available sources do not mention FDA approval for any parasitic infections beyond strongyloidiasis and onchocerciasis.
7. Practical takeaways for patients and clinicians
If you or a clinician are considering ivermectin, rely on FDA‑approved indications and the product label for dosing (weight‑based: roughly 200 mcg/kg for strongyloidiasis; 150–200 mcg/kg regimens for onchocerciasis and public‑health use), avoid veterinary products, and treat other parasitic or dermatologic conditions as off‑label uses requiring clinical judgment [3] [4] [6]. Where sources disagree — for example, state laws making OTC human ivermectin available — those are policy developments separate from FDA approval and do not broaden the FDA’s labeled indications [9] [12].
Limitations: this summary uses the provided sources only; it does not attempt to adjudicate emerging off‑label research nor to substitute for individual prescribing decisions. All factual claims above are cited to the documents listed [6] [1] [2] [9] [4] [5] [3] [8].