What are standard single-dose ivermectin regimens for common parasitic infections (strongyloidiasis, onchocerciasis, scabies)?
Executive summary
Single‑dose ivermectin regimens commonly cited for these infections are: ~200 µg/kg once for uncomplicated strongyloidiasis (with some trials using two 200 µg/kg doses 2 weeks apart or repeat dosing in immunocompromised patients) [1] [2] [3]. For onchocerciasis, programs and trials use a single 150 µg/kg oral dose, usually repeated annually (or more frequently in mass campaigns) [4] [5]. For ordinary scabies, clinical guidance generally favors two 200 µg/kg oral doses spaced 7–14 days apart rather than a single dose; crusted scabies requires multiple doses plus topical therapy [6] [7] [8].
1. Strongyloidiasis: a single 200 µg/kg dose is the practical standard
Clinical regulators and trials identify ivermectin ~200 micrograms per kilogram as the standard single‑dose treatment for uncomplicated intestinal strongyloidiasis: the marketed tablet label recommends a single oral dose to provide approximately 200 µg/kg (Stromectol label) [1]. Large randomized trials and reviews concluded a single dose is sufficient for non‑disseminated disease and better tolerated than multidose regimens [2] [9]. Some studies show higher cure rates when the 200 µg/kg dose is repeated (either a second single dose two weeks later or short multi‑day regimens), and experts advise retreatment or suppressive monthly therapy in immunocompromised patients or when follow‑up stool tests remain positive [3] [10] [11]. National guidance (CDC, other reviews) recommends 200 µg/kg daily for 1–2 days as first‑line and stresses follow‑up testing because persistent or disseminated infection requires different management [12] [11].
2. Onchocerciasis (river blindness): 150 µg/kg single dose for control; repeated mass dosing for elimination
Historical and programmatic literature shows a single 150 µg/kg oral dose of ivermectin is the standard microfilaricidal regimen for onchocerciasis; that single dose reduces skin microfilariae and ocular disease and has been the backbone of annual mass drug administration (MDA) programs [4] [13]. WHO/APOC strategies rely on annual community‑directed treatment (usually to those aged ≥5 years) and in some foci use biannual or more frequent rounds to accelerate elimination; dosing is the same per round, but frequency and duration vary by epidemiology [5] [14]. Important limitation: ivermectin kills microfilariae but does not reliably kill adult Onchocerca volvulus, so repeat rounds over many years are required to interrupt transmission [15] [16].
3. Scabies: two doses of 200 µg/kg spaced 1–2 weeks apart is the clinical norm; crusted disease needs many doses plus topical agents
For ordinary (classical) scabies, public health guidance (CDC and multiple guidelines) reports that ivermectin is usually given as 200 µg/kg per dose and that two doses given 7–14 days apart are standard when oral therapy is chosen; single‑dose regimens perform less well for routine scabies because the first dose kills mites but not eggs [6] [17]. For crusted (severe) scabies, protocols combine topical permethrin with multiple ivermectin doses (various regimens: 3–7 doses over weeks) because parasite burden and treatment failure risk are high [7] [8]. Regulatory status varies: ivermectin is not FDA‑approved for scabies in the U.S., though many countries authorize two‑dose programs and mass treatment campaigns use ivermectin effectively [6] [18].
4. Where guidance diverges and important caveats
Trials disagree on whether single versus multiple doses are superior for strongyloidiasis in special populations; the multicenter StrongTreat trial supported single‑dose use in non‑disseminated infections, yet other studies report improved cure with repeated or multi‑day dosing and recommend repeat/suppressive therapy in immunocompromised hosts [2] [3] [10]. For onchocerciasis the per‑person dose (150 µg/kg) is stable, but elimination programs vary frequency (annual vs biannual) based on modelling and field results [16] [14]. For scabies, many national guidelines, reviews and RCTs favour two 200 µg/kg doses one week apart, but single‑dose regulatory labels in some countries still exist and some trials have tested higher single doses [19] [20] [21].
5. Practical implications and monitoring
Clinicians should follow local/national guidance and weight‑based dosing, perform follow‑up testing for strongyloidiasis (retest stool/serology) when indicated, and consider repeated or suppressive therapy in immunosuppressed patients [11] [12]. For onchocerciasis, expect repeated community rounds rather than a one‑time cure and be aware of contraindications where Loa loa co‑infection risks severe adverse events [15] [22]. For scabies, use combined topical/oral approaches for crusted cases and treat contacts and the environment as advised by public health guidance [6] [8].
Limitations: available sources do not mention specific pediatric dose adjustments for all ages beyond weight bands nor do they provide a single universal “one‑size” regimen for immunocompromised or pregnant patients; consult infectious disease or tropical medicine experts and national formularies for those scenarios (not found in current reporting).