What are the recommended weight‑based ivermectin dosing schedules for common parasitic infections?
Executive summary
Ivermectin dosing for human parasitic infections is weight‑based and typically ranges from about 150 to 400 micrograms per kilogram (mcg/kg) depending on the pathogen, the clinical scenario, and public‑health use; common regimens include 200 mcg/kg as a single oral dose for strongyloidiasis and ~150–200 mcg/kg for onchocerciasis with periodic retreatment [1] [2] [3]. Practical administration (fasted vs with food), repeat intervals, and higher doses used in filariasis or mass campaigns are important variables; safety concerns—especially in regions with Loa loa—must shape clinician decision‑making [3] [2] [4].
1. How the weight‑based recommendations map to specific infections
Strongyloidiasis is commonly treated with a single oral dose of ivermectin at about 200 mcg/kg, which is the standard cited by drug guides and clinical summaries [1] [3]; onchocerciasis regimens commonly use 150–200 mcg/kg as a single dose, often repeated on an annual or similarly spaced programmatic schedule because ivermectin clears microfilariae but does not reliably kill adult worms [5] [2] [3]. Lymphatic filariasis protocols cited in reviews and mass‑treatment reports use higher ivermectin dosing—around 400 mcg/kg (0.4 mg/kg) in combined regimens for community programs—rather than the lower single‑dose regimens used for intestinal nematodes [2] [6]. For many cutaneous parasitic infestations, including routine scabies, published practical guides report single doses near 200 mcg/kg with a repeat dose after approximately two weeks; crusted scabies requires multiple, staged doses combined with topical therapy [7] [8].
2. Practical dosing, tablet math, and administration
Commercial human tablets are most often 3 mg each, and standard dosing tables are designed to deliver approximately 150–200 mcg/kg per the FDA label and major formularies, meaning clinicians calculate total milligrams by weight and round to whole tablets per available guidance [3] [5]. The FDA label notes Stromectol was designed to provide roughly 200 mcg/kg and recommends taking tablets on an empty stomach with water for the systemic helminth indications, whereas dermatology sources advise that dosing for scabies may be given with food to improve bioavailability and epidermal penetration—an important practical difference [3] [7].
3. Repeat dosing, programmatic schedules, and verification
Single doses often suffice for intestinal strongyloidiasis, but follow‑up testing (stool exams) is recommended to document eradication, and onchocerciasis typically requires repeated community or annual dosing because ivermectin has limited activity against adult Onchocerca worms [3] [6]. Mass‑treatment campaigns and refugee presumptive protocols combine ivermectin with other anthelmintics and may use fixed annual dosing (for example, 0.4 mg/kg yearly in some filariasis control studies) rather than single episodic prescriptions, reflecting program objectives rather than individualized therapy [6] [9].
4. Safety, special situations, and controversy
Ivermectin has a generally favorable safety profile in approved uses, but higher doses correlate with more adverse events—ocular complications have been reported at increased dosages, and severe neurological reactions are documented in special circumstances (notably in patients with high Loa loa microfilarial loads) so clinicians screen travel histories and endemic exposures before use in some regions [2] [4]. Regulatory and clinical sources highlight that ivermectin is approved for specific parasitic infections and is not indicated for other conditions such as COVID‑19; misuse and veterinary product errors remain safety risks [5] [10] [4]. Where guidance differs—fasted versus fed dosing, single versus repeated administration, or 150 versus 200 mcg/kg—clinicians rely on indication, patient factors, and local public‑health policy [3] [7] [2].
5. Bottom line for clinicians and programs
Use weight‑based dosing: roughly 200 mcg/kg single dose for strongyloidiasis, 150–200 mcg/kg for onchocerciasis with repeated programmatic dosing as required, and up to 400 mcg/kg in certain filariasis mass‑treatment settings; adjust regimen frequency and administration conditions by indication and follow established guidance [1] [2] [3] [6]. When evidence or guidance diverges, prefer indication‑specific regulatory labels and specialist guidelines, verify eradication where appropriate, and account for regional risks like Loa loa that mandate caution [3] [6] [4].