Stromectol Dosage for Humans

Stromectol (ivermectin) is a broad-spectrum antiparasitic tablet used to treat several human parasitic infections, most notably strongyloidiasis and onchocerciasis. Because dosing is weight-based rather than one-size-fits-all, getting the numbers right matters. Under-dosing risks treatment failure and persistent infection, while over-dosing can cause neurological and gastrointestinal side effects. This guide explains the recommended ivermectin dosing schedule for humans, breaking down the calculations by body weight, indication, age, and special populations so both patients and clinicians can cross-check what has been prescribed.

Ivermectin is only available with a prescription in most countries, and self-medication is strongly discouraged. The information below is educational and reflects the labeling used by regulatory agencies and standard tropical-medicine references. Always follow the specific instructions given by a qualified prescriber.

How Stromectol Dosing Works

Stromectol is supplied as 3 mg scored tablets. Dosing is calculated in micrograms per kilogram of body weight (µg/kg or mcg/kg), then rounded to the nearest whole tablet. Two dose bands are used in almost every human indication:

150 µg/kg, the lower band, used for onchocerciasis (river blindness).
200 µg/kg, the standard band, used for strongyloidiasis and most other approved indications.
Higher, repeated dosing (200 µg/kg on days 1, 2, 8, 9, 15, and sometimes 22 and 29), used for severe or crusted (Norwegian) scabies in combination with topical therapy.

Because tablets are 3 mg and cannot be split into micrograms precisely, dose bands are converted into a tablet count by weight range. This gives the familiar dosing tables found on the product label.

Stromectol Dose by Body Weight (Quick Reference Table)

The table below shows the number of 3 mg tablets for the two most common dosing bands. It matches the structure used on the U.S. FDA-approved label.

Body weight	Onchocerciasis (150 µg/kg)	Strongyloidiasis & standard indications (200 µg/kg)
15–24 kg (33–53 lb)	1 tablet (3 mg)	— (see pediatric note)
15–25 kg	—	1 tablet (3 mg)
25–35 kg	1 tablet (3 mg)	2 tablets (6 mg)
26–44 kg (57–97 lb)	2 tablets (6 mg)	—
36–50 kg	2 tablets (6 mg)	3 tablets (9 mg)
45–64 kg (99–141 lb)	3 tablets (9 mg)	—
51–65 kg	3 tablets (9 mg)	4 tablets (12 mg)
65–79 kg	4 tablets (12 mg)	5 tablets (15 mg)
65–84 kg (143–185 lb)	4 tablets (12 mg)	—
≥85 kg (≥187 lb)	150 µg/kg exact	—
≥80 kg	—	200 µg/kg exact (approx. 1 tab per 15 kg)

For patients above the top of the chart, use the microgram-per-kilogram formula directly. Example: a 92 kg adult treated for strongyloidiasis at 200 µg/kg requires 18.4 mg, which rounds to six 3 mg tablets (18 mg), the closest whole-tablet dose without exceeding the calculated amount by more than about 10%.

Dosing by Indication

Strongyloidiasis (intestinal Strongyloides stercoralis)

Dose: 200 µg/kg as a single oral dose.
Follow-up: stool examinations should be repeated for several months; a second treatment course may be needed if larvae persist.
Immunocompromised patients: hyperinfection syndrome requires prolonged, repeated dosing (often daily for 1–2 weeks) under specialist care, sometimes combined with albendazole.

Onchocerciasis (river blindness, Onchocerca volvulus)

Dose: 150 µg/kg as a single oral dose.
Frequency: repeated every 6 to 12 months until adult worms die (typically 10–15 years); ivermectin kills microfilariae but not adult worms.
Contraindication caveat: in areas co-endemic with Loa loa, screening for high microfilarial load is required because of the risk of severe post-treatment encephalopathy.

Scabies (classical)

Dose: 200 µg/kg orally, repeated after 7–14 days.
Combining with topical permethrin 5% improves cure rates.

Crusted (Norwegian) scabies

Dose: 200 µg/kg on days 1, 2, 8, 9, and 15, extended to days 22 and 29 in severe cases, always combined with topical scabicide and keratolytic therapy.

Pediculosis (head lice), when oral therapy is chosen

Dose: 200–400 µg/kg, repeated after 7 days. Topical treatment is preferred first-line in most guidelines.

Cutaneous larva migrans, ascariasis, trichuriasis, enterobiasis

Dose: typically 200 µg/kg single dose; occasionally repeated. These are off-label in some jurisdictions but well supported in tropical-medicine literature.

How to Take Stromectol

Take tablets on an empty stomach with water, at least one hour before food, according to the historic FDA label. One note: bioavailability is roughly 2.5× higher when taken with a fatty meal, and some newer guidelines and WHO practice allow administration with food, particularly for scabies where higher tissue levels are desirable. Follow your prescribers instruction.
Do not crush or chew the tablets unnecessarily; they are stable and easy to swallow whole.
Missed dose: if the treatment is a single dose and it was missed, take it as soon as possible. For multi-day scabies schedules, take the missed tablet on the same day if remembered; if the entire day is missed, resume the schedule and inform the prescriber.

Dosing in Special Populations

Children

Ivermectin is approved in patients weighing at least 15 kg (roughly age 5 and older, though weight is the deciding factor, not age). Safety data below 15 kg are limited, and use in this group should only occur under specialist supervision. Dosing by weight is identical to adult calculations.

Elderly patients

No specific dose reduction is required based on age alone. However, elderly patients more often have comorbidities, polypharmacy, or reduced hepatic clearance, all of which warrant careful review before prescribing.

Pregnancy and breastfeeding

Pregnancy: ivermectin is classified as Category C in the older FDA system. It is generally avoided in pregnancy unless the benefit clearly outweighs the risk. Mass drug administration programs typically exclude pregnant women.
Breastfeeding: small amounts pass into breast milk. WHO considers it compatible with breastfeeding when clinically necessary, but the manufacturer advises caution.

Renal and hepatic impairment

No formal dose adjustment is defined, but caution is advised in significant hepatic impairment because ivermectin is metabolized in the liver by CYP3A4.

Drug interactions

Strong CYP3A4 inhibitors (e.g., ritonavir, ketoconazole) can increase ivermectin levels. Warfarin has been reported to have an enhanced anticoagulant effect in some cases. Combining with other CNS-depressant medications is generally not a problem, but caution is prudent. For a detailed pharmacology profile, the pharmacokinetic entry on ivermectin in DrugBank is a solid reference.

Side Effects and What to Watch For

At approved human doses, ivermectin is generally well tolerated. Most reactions are mild and often reflect the immune response to dying parasites rather than the drug itself (the Mazzotti reaction, seen especially in onchocerciasis).

Common (up to about 10%):

Fatigue, drowsiness, dizziness
Nausea, mild abdominal pain, diarrhea
Itching, transient rash
Mild fever, headache
Joint and muscle aches

Less common but important:

Postural hypotension
Tachycardia
Peripheral edema, facial edema
Lymph node tenderness

Rare, serious:

Severe skin reactions (Stevens–Johnson syndrome, toxic epidermal necrolysis)
Hepatitis, elevated transaminases
Encephalopathy, particularly in Loa loa co-infection
Seizures

Seek urgent medical care for chest pain, difficulty breathing, confusion, severe rash, jaundice, or seizures.

Signs of Overdose

Accidental overdose, most often reported when veterinary formulations intended for horses or cattle are ingested, can cause:

Severe nausea, vomiting, diarrhea
Ataxia (loss of coordination), tremor
Hypotension, tachycardia
Mydriasis (dilated pupils), visual disturbance
Sedation progressing to stupor, seizures, coma in extreme cases

Treatment is supportive; there is no specific antidote. Poison control should be contacted immediately for any suspected overdose. Veterinary ivermectin products should never be used in humans, because concentrations, excipients, and pharmaceutical quality standards are not appropriate.

Practical Dosing Examples

To make the tables concrete, three worked examples:

A 68 kg adult with confirmed strongyloidiasis.
Calculation: 68 × 200 = 13,600 µg = 13.6 mg → 4 tablets (12 mg) or 5 tablets (15 mg). The label uses 4 tablets for 65–79 kg.
A 22 kg child (age 7) treated for scabies.
Calculation: 22 × 200 = 4,400 µg = 4.4 mg → 1 tablet (3 mg), the closest whole-tablet dose. Repeat in 7–14 days.
A 90 kg adult in an onchocerciasis program.
Calculation: 90 × 150 = 13,500 µg = 13.5 mg → 4 tablets (12 mg), repeated every 6 or 12 months per program schedule.

Storage and Handling

Store below 30 °C (86 °F) in the original container.
Keep out of reach of children. Pediatric accidental ingestion of adult-dose tablets can produce significant toxicity.
Do not use tablets past their expiry date; ivermectin degrades slowly, but potency assurance ends at expiry.

When Not to Use Stromectol

Known hypersensitivity to ivermectin or excipients.
Weight under 15 kg (unless directed by a specialist).
Suspected or confirmed high-load Loa loa co-infection without prior screening.
Unproven indications (for example, viral respiratory infections). Multiple large randomized trials have failed to show benefit for such uses, and taking ivermectin outside approved indications exposes patients to risk without benefit. Guidance from the WHO position on ivermectin for COVID-19 remains the most-cited public health statement on this point.

Key Takeaways

The Stromectol dosage for humans is weight-based: 150 µg/kg for onchocerciasis and 200 µg/kg for strongyloidiasis and most other indications.
Dosing tables convert body weight to whole 3 mg tablets; above the top of the chart, calculate by µg/kg.
Most indications require a single dose, but scabies and crusted scabies need repeat doses.
Approved in patients ≥15 kg; avoid in pregnancy unless clearly indicated.
Never substitute veterinary formulations, and never self-prescribe.

FAQ

How many Stromectol tablets should an average adult take?

For a typical 70 kg adult treated at 200 µg/kg (for example, for strongyloidiasis or scabies), the dose is 14 mg, rounded to four to five 3 mg tablets, taken as a single dose. For onchocerciasis at 150 µg/kg, the same adult would take 10.5 mg, which rounds to four tablets (12 mg) per the standard weight-band table.

Can Stromectol be taken with food?

The original label specifies an empty stomach with water. However, food, especially fatty food, increases absorption roughly 2.5-fold, which is sometimes exploited to improve efficacy in scabies. Take it exactly as your prescriber directs and stay consistent across doses if a multi-day course is prescribed.

Do I need to repeat the dose?

It depends on the indication. Strongyloidiasis and onchocerciasis are usually treated with a single dose (though onchocerciasis is repeated every 6–12 months for years). Scabies typically requires a second dose after 7–14 days, and crusted scabies requires several doses over 2–4 weeks combined with topical therapy.

Is Stromectol safe for children?

Ivermectin is considered safe and effective in children weighing 15 kg or more, using the same weight-based dosing as adults. Use below 15 kg lacks robust safety data and should only be considered under specialist supervision.