What are the recommended ivermectin dosing schedules for onchocerciasis and strongyloidiasis?
Executive summary
Ivermectin dosing for onchocerciasis and strongyloidiasis is well established: onchocerciasis is typically treated with a single 150 micrograms per kilogram (mcg/kg) oral dose given at intervals (commonly annually) to suppress skin microfilariae, while uncomplicated intestinal strongyloidiasis is usually treated with a single 200 mcg/kg oral dose (with retreatment or repeat courses in some patients) [1] [2] [3].
1. Onchocerciasis — the standard suppression schedule
Clinical trials and program experience support a single oral dose of approximately 150 mcg/kg of ivermectin as the routine regimen for onchocerciasis, with that single dose repeated on a programmatic schedule (commonly every 6–12 months, and often once yearly in mass treatment campaigns) because ivermectin is microfilaricidal but has limited effect on adult Onchocerca volvulus parasites [1] [4] [5].
2. Strongyloidiasis — single-dose therapy with caveats
For uncomplicated intestinal Strongyloides stercoralis infection, most drug labels and clinical reviews recommend a single 200 mcg/kg oral dose as the usual effective regimen, with many studies and guidelines reporting cure after one dose; some older trials and practice patterns cite 150–200 mcg/kg as acceptable and retreatment or a second dose may be given if initial therapy fails [2] [3] [6] [7].
3. When a single dose is not enough — repeat dosing and special populations
Immunocompromised patients, those with disseminated strongyloidiasis, or patients with treatment failure may require repeated courses, more frequent dosing (for example, repeat doses at two-week intervals), or even monthly suppressive therapy; similarly, onchocerciasis requires repeated dosing over years because ivermectin does not kill adult worms and only temporarily suppresses microfilariae [5] [3] [7]. Clinical guidance and product labeling also warn about serious inflammatory reactions (the Mazzotti reaction) and rare severe neurologic events in some contexts, so monitoring and specialist input are important when treating heavily infected or vulnerable patients [1] [8].
4. Public‑health scheduling — mass drug administration and program practice
Onchocerciasis control programs and WHO-supported mass drug administration (MDA) campaigns commonly use annual or semiannual ivermectin distribution at the microdose recommended for onchocerciasis, and WHO has extensive experience recommending ivermectin in MDA packages both for onchocerciasis and, in some contexts, to reduce strongyloidiasis prevalence; dose selection in MDA balances individual efficacy with safety and operational feasibility [9] [1].
5. Practical points, variations, and where guidance diverges
Product labeling and clinical references show some variation — FDA labeling and many clinical sources emphasize 150–200 mcg/kg ranges for onchocerciasis and 200 mcg/kg for strongyloidiasis, while dermatology and other specialty references sometimes recommend 150–250 mcg/kg or repeat doses at day 7–14 for related parasitic diseases; ivermectin is usually dosed by body weight, tablets are taken orally (often on an empty stomach for these intestinal indications), and heavier or complicated infections require individualized clinical judgment [2] [10] [11] [4].
6. Bottom line and clinical implications
The pragmatic, evidence-rooted summary is: for onchocerciasis, give a single ~150 mcg/kg oral dose and repeat on the programmatic schedule (commonly every 6–12 months); for uncomplicated intestinal strongyloidiasis, a single 200 mcg/kg oral dose is typical, with retreatment or longer suppressive strategies for immunocompromised or refractory cases — but clinicians must tailor therapy to severity, co‑infections, and the risk of inflammatory reactions, and follow local guidelines and product labeling [1] [2] [3] [5].