How is ivermectin dosage calculated by weight for pediatric and adult patients?
Executive summary
Ivermectin dosing for humans is weight‑based: commonly 150 micrograms (0.15 mg) per kg for onchocerciasis and about 200 micrograms (0.2 mg) per kg for strongyloidiasis; many clinical references and product labels express the usual single oral tablet dose as 0.15–0.2 mg/kg [1] [2] [3]. Practical tablet charts convert those mg/kg targets into 3 mg tablet counts (e.g., 15–25 kg ≈ 3 mg, 26–44 kg ≈ 6 mg, 45–64 kg ≈ 9 mg, 65–84 kg ≈ 12 mg) in dosing guides such as Drugs.com and product labeling [4] [3] [1].
1. How clinicians calculate a dose: weight to micrograms to tablets
Standard practice is to calculate the patient’s weight in kilograms, multiply by the target dose in micrograms per kilogram (commonly 150 mcg/kg for onchocerciasis, 200 mcg/kg for strongyloidiasis), convert micrograms to milligrams, and then prescribe the nearest number of available 3 mg tablets to deliver that total [1] [2] [3]. For example, a 70 kg adult at 200 mcg/kg would require 14 mg (70 × 0.2 mg = 14 mg), commonly given as 4 tablets of 3 mg (12 mg) or adjusted per prescribing guidance and clinical judgment [2] [3]. Drugs.com and other clinical references present ready charts translating weight bands into tablet counts for usability [4] [3].
2. Differences by indication: why the mcg/kg target varies
Dose targets differ by parasite: the FDA label and prescribing references specify approximately 150 mcg/kg for onchocerciasis (river blindness) and 200 mcg/kg for strongyloidiasis; dosing recommendations are indication‑specific on product labeling and drug references [1] [5]. Clinical practice and summary resources thus list a typical single dose range of about 0.15–0.25 mg/kg depending on the condition being treated [6] [3].
3. Pediatric considerations and minimum weight thresholds
Most human ivermectin guidance applies to adults and children weighing at least 15 kg; the Mayo Clinic and product information state doses are based on body weight and that children must meet minimum weight thresholds before tablets are used, with the usual dose quoted as 200 mcg/kg for many indications [2] [1]. Practical dosing charts (e.g., Drugs.com) provide tablet counts by pediatric weight bands (15–25 kg → 3 mg; 26–44 kg → 6 mg; etc.) to help clinicians avoid complex calculations when tablets are the formulation available [4] [3].
4. Single‑dose vs repeat or high‑dose regimens — what sources say
For many parasitic infections a single oral dose is standard, but some conditions require repeat dosing or different schedules: onchocerciasis mass‑treatment programs often use 0.15 mg/kg annually (with retreatment intervals varying), crusted scabies may require multiple doses spaced 1–2 weeks, and some protocols use monthly suppressive therapy for difficult strongyloidiasis cases; these variations are described in clinical references [4] [3]. Separate research trials have investigated higher or repeated dosing (e.g., up to and above usual mcg/kg targets) for other uses, but standard prescribing documents remain the primary guidance [7].
5. Safety, formulation limits and practical caveats
Product labels and clinical resources warn that ivermectin is metabolized in the liver, requires caution in hepatic disease, can cause neurologic adverse events with overdose, and that dosing should follow a prescriber’s instructions—“never take larger amounts” than recommended [3] [5]. Tablet strength (commonly 3 mg per tablet) constrains exact dosing; clinicians typically round to practical tablet counts while aiming to approximate the mcg/kg target [2] [3].
6. Points of disagreement, off‑label use and sources to watch
Most mainstream references (FDA product labeling, Mayo Clinic, Drugs.com, Medscape) align on weight‑based dosing (150–200 mcg/kg) and provide the same practical tablet charts [1] [2] [3]. Some secondary sources and advocacy groups publish alternative calculators or higher suggested regimens; independent calculators and non‑clinical guides exist but are not reflected in FDA labeling or primary clinical references cited here [8] [9]. Available sources do not mention specific COVID‑19 dosing recommendations as valid clinical guidance—Medically reviewed pages note ivermectin is not approved for COVID‑19 and dosing for that purpose is not recommended [10].
Limitations: this summary uses only the supplied sources and does not substitute for individual clinical judgment. For a patient‑specific dose, clinicians must use current product labeling and local guidance and verify weight and indication before prescribing [1] [2].