Stromectol vs Generic Ivermectin: FDA-Approved Generics, Dosing and What It Treats

Stromectol is Merck's brand of ivermectin tablets. In the US it has had FDA-approved generic competition since 2014, and there are now seven approved generic makers. Outside the US, ivermectin is sold under dozens of brand names, including 12 mg and higher strengths that Stromectol never came in. Knowing which of these is equivalent to Stromectol, and which is simply "ivermectin from somewhere", matters more than the brand name.

This guide compares Stromectol with generic ivermectin using the FDA's own approval records and the Stromectol prescribing information: what the generics are, what "AB rated" means, how the dose is worked out, what the drug is approved for, and what it is not.

The short answer

FDA-approved generic ivermectin 3 mg tablets are rated therapeutically equivalent (AB) to Stromectol. They contain the same drug at the same strength and have been shown to be bioequivalent, with blood levels within the FDA's accepted range of Stromectol's, so they can be expected to work the same way. Stromectol and its US generics are approved for two parasitic infections: intestinal strongyloidiasis and onchocerciasis (river blindness). Imported brands such as Ivercor, Iverguard or Iverheal contain ivermectin but are not FDA-approved, so equivalence depends on the manufacturer. Ivermectin tablets are not an effective treatment for outpatients with mild to moderate COVID-19: two large randomised trials, with three placebo comparisons, found no benefit.

What Stromectol is

• Maker: Merck Sharp and Dohme (FDA application NDA 050742, approved November 1996).
• Tablet: 3 mg ivermectin, white, round, coded MSD on one side and 32 on the other. A 6 mg Stromectol tablet was discontinued, and the FDA recorded that this was not for safety or effectiveness reasons.
• Approved uses: intestinal strongyloidiasis caused by Strongyloides stercoralis, and onchocerciasis caused by Onchocerca volvulus.
• Prescription status: prescription only in the US.

Ivermectin was developed from avermectins, compounds made by a soil bacterium, and it works by paralysing susceptible worms. It is metabolised mainly by the liver enzyme CYP3A4, has a plasma half-life of about 18 hours, and is excreted almost entirely in the stool over an estimated 12 days.

FDA-approved generic ivermectin

The FDA's approval database lists these ivermectin tablets for the US market:

Application	Maker	Strength	FDA equivalence rating	Approved
NDA 050742 (Stromectol)	Merck Sharp and Dohme	3 mg	AB (reference product)	November 1996
ANDA 204154	Edenbridge Pharmaceuticals	3 mg	AB	October 2014
ANDA 218324	Senores Pharmaceuticals	3 mg	AB	October 2024
ANDA 215922	Rubicon Research	3 mg and 6 mg	AB for 3 mg; none listed for 6 mg	January 2025
ANDA 218805	Epic Pharma	3 mg	AB	September 2025
ANDA 216863	Zydus Lifesciences	3 mg	AB	February 2026
ANDA 216808	E5 Pharma	3 mg	AB	March 2026
ANDA 218509	Ajanta Pharma	3 mg	AB	April 2026

Dates are the original approval dates in the FDA database. No equivalence rating is listed for the 6 mg generic, which is currently the only 6 mg ivermectin tablet marketed in the US; the 6 mg Stromectol has been discontinued.

What "AB rated" means

An AB rating is the FDA's statement that a generic is therapeutically equivalent to the reference product. To earn it, a generic must contain the same active ingredient at the same strength and in the same dosage form, and it must have shown bioequivalence: blood levels of the drug that fall within the FDA's accepted range of the brand's.

In practice, that means a pharmacist in the US can substitute an AB-rated generic for Stromectol, and you can expect the same results and the same side effects. What can differ is the tablet's appearance, its inactive ingredients and the price.

Imported ivermectin brands

Outside the US, ivermectin tablets are made by many companies, often in strengths of 3, 6, 12 mg and higher. SafeRxPills sells several, including Ivercor 3 mg, Ivercor 6 mg and Ivercor 12 mg.

We are direct about the difference. These products are not FDA-approved, and they do not carry an AB rating against Stromectol. The FDA has not reviewed their bioequivalence. Their quality depends on the manufacturer's standards, such as WHO GMP certification, and on the supply chain. Our guide to what WHO GMP certification means covers what that does and does not guarantee.

The larger strengths bring one practical advantage and one risk. A 12 mg tablet covers many adults' strongyloidiasis dose in one tablet instead of four. But very high strengths, such as 40 mg or 80 mg tablets, are far above what the label dose requires for almost anyone. At 200 mcg/kg, an 80 mg dose would be the calculated dose for a person weighing 400 kg. Our high dose ivermectin guide explains why more is not better.

Stromectol and generics compared

Feature	Stromectol	FDA-approved generic	Imported, not FDA-approved
Active ingredient	Ivermectin	Ivermectin	Ivermectin
US strength	3 mg	3 mg (one maker also 6 mg)	Often 3, 6, 12 mg or higher
Bioequivalence reviewed by FDA	Reference product	Yes, AB rated	No
Approved uses in the US	Strongyloidiasis, onchocerciasis	Same	Not approved in the US
US prescription needed	Yes	Yes	Yes in the US, whatever the source; unapproved imports are not FDA-authorised. Rules elsewhere vary

How well it works for strongyloidiasis

Strongyloidiasis is an intestinal threadworm infection that can persist for decades and become dangerous in people with weakened immunity. The Stromectol label reports five comparative studies of a single ivermectin dose of 170 to 200 mcg/kg.

Study	Ivermectin, cured	Comparison drug, cured
International study vs albendazole 200 mg twice daily for 3 days	24 of 26 (92%)	12 of 22 (55%)
WHO study vs albendazole	126 of 152 (83%)	67 of 149 (45%)
International study vs thiabendazole 25 mg/kg twice daily for 3 days	9 of 14 (64%)	13 of 15 (87%)
US studies vs thiabendazole	14 of 14 (100%)	16 of 17 (94%)

Across the comparative and open studies, the label summarises cure as 64% to 100% after a single 200 mcg/kg dose. Ivermectin was better tolerated than thiabendazole, though patients reported more abdominal distension and chest discomfort than on albendazole.

Checking that treatment worked

A single dose often cures strongyloidiasis, but cure needs checking. In a French study where reinfection was impossible, some patients had larvae reappear in their stool up to 106 days after treatment. The label advises at least three stool examinations over the three months after treatment, and retreatment if larvae return. People with weakened immune systems, including HIV infection, may need repeated courses, sometimes every two weeks, and cure may not be achievable.

How well it works for onchocerciasis

Onchocerciasis, or river blindness, is caused by a worm spread by blackflies, mainly in Africa. In a placebo-controlled study of adults with moderate to severe infection, a single dose of 150 mcg/kg reduced skin microfilariae (the worm's larvae) by 83.2% at day 3 and 99.5% at month 3, with a reduction of more than 90% lasting up to 12 months.

Ivermectin kills the larvae but not the adult worms, so retreatment is usually required. The label notes that mass treatment programmes most often use a 12 month interval, and that individual patients may be retreated as often as every 3 months. Side effects in onchocerciasis are mainly Mazzotti reactions to dying larvae, covered in our ivermectin side effects guide.

Working out the dose

The dose is based on body weight: about 200 mcg per kg for strongyloidiasis and about 150 mcg per kg for onchocerciasis, as a single dose. The label converts this into numbers of 3 mg tablets.

Strongyloidiasis: body weight	3 mg tablets	Onchocerciasis: body weight	3 mg tablets
15 to 24 kg	1	15 to 25 kg	1
25 to 35 kg	2	26 to 44 kg	2
36 to 50 kg	3	45 to 64 kg	3
51 to 65 kg	4	65 to 84 kg	4
66 to 79 kg	5	85 kg or more	150 mcg/kg
80 kg or more	200 mcg/kg

Safety and effectiveness have not been established in children under 15 kg. Our ivermectin dosage guide covers other uses and strengths.

Take it on an empty stomach

The label says to take ivermectin on an empty stomach with water. Food changes how much is absorbed: in a pharmacokinetic study, 30 mg taken after a high fat meal gave about 2.5 times the exposure of the same dose taken fasting. That is a reason to follow the label rather than a way to boost the dose, since higher exposure means more risk of side effects.

Other ivermectin products

Ivermectin also comes in forms that are not substitutes for Stromectol tablets:

• Ivermectin 1% cream (Soolantra in the US) is approved for the bumps and pimples of rosacea. It is applied to the skin and does not treat worm infections. See our ivermectin for rosacea guide.
• Ivermectin 0.5% lotion (Sklice) is approved for head lice.
• Veterinary ivermectin pastes, injectables and pour-ons are made for animals, at concentrations and with ingredients not intended for people. Our horse paste guide explains why they are not a substitute.

Scabies and other uses not on the label

In the US, oral ivermectin is not approved for scabies, head lice or other parasites, although doctors sometimes prescribe it off label for them. Our ivermectin for scabies guide covers the dosing doctors use. Off-label use should be guided by a doctor, especially because some parasites need repeat doses and some patients need a different drug.

What the COVID-19 trials showed

Ivermectin was widely promoted for COVID-19. Two large randomised, placebo-controlled trials in outpatients tested it properly, one of them at two different doses.

Trial	Patients	Dose	Main result
TOGETHER (Brazil), NEJM 2022	679 ivermectin, 679 placebo, adults with a risk factor for severe disease	400 mcg/kg daily for 3 days	Hospital admission or prolonged emergency observation: 14.7% vs 16.3% (relative risk 0.90, 95% credible interval 0.70 to 1.16)
ACTIV-6 (US), first ivermectin arm, JAMA 2022	817 ivermectin, 774 placebo	400 mcg/kg daily for 3 days	Median time to recovery 12 vs 13 days, not significant; hospitalisation or death 1.2% in both groups
ACTIV-6 (US), second ivermectin arm, JAMA 2023	602 ivermectin, 604 placebo	Up to 600 mcg/kg daily for 6 days	Median time to recovery 11 days in both groups; hospitalisation, death or urgent care 5.7% vs 6.0%

Both ACTIV-6 reports concluded that the findings do not support using ivermectin for mild to moderate COVID-19. The doses tested were two to three times the strongyloidiasis dose and given for several days, with no benefit. None of these trials studied people admitted to hospital.

Side effects and safety

At the approved doses, ivermectin is usually well tolerated. In strongyloidiasis trials, each side effect was reported by fewer than 3% of patients, the most common being dizziness and itching (2.8% each), then diarrhoea and nausea. In onchocerciasis, reactions to dying larvae are common in the first days. Important safety points from the label:

• Loa loa: people with heavy Loa loa infection, found in parts of Central and West Africa, can rarely develop a serious or fatal brain reaction after treatment. Anyone who has lived in those areas should be checked first.
• Neurotoxicity: Merck's current label (revised September 2024) also reports altered consciousness from drowsiness to coma, confusion and disorientation in people without Loa loa, and deaths have been reported, at recommended doses as well as in overdose. These reactions generally resolved after stopping ivermectin with supportive care. Stop and get help for any confusion or unusual drowsiness.
• Warfarin: increased INR has been rarely reported when ivermectin was taken with warfarin.
• Pregnancy: ivermectin caused birth defects in animal studies at or near doses toxic to the mother. The label says it should not be used during pregnancy because safety has not been established.
• Breastfeeding: ivermectin passes into breast milk in low concentrations.

The full side effect data, by indication, are in our ivermectin side effects guide.

Brand or generic: which to choose

• In the US with a prescription: an AB-rated generic is the rational choice. It is interchangeable with Stromectol by FDA standards.
• Buying outside the US system: choose a product whose maker, strength, batch and expiry are clearly shown, from a seller who will answer questions about them. Pick a strength that fits your weight-based dose rather than the biggest tablet.
• Whatever you buy: ivermectin treats specific parasites. Get the infection diagnosed, because other worms need other drugs and some infections need follow-up testing.

When to see a doctor

See a doctor before taking ivermectin if you are pregnant, could be pregnant or are breastfeeding, take warfarin, have a weakened immune system, or have lived in Central or West Africa. See one after treatment if symptoms do not settle, if you develop confusion, severe dizziness or difficulty walking, or if stool tests show larvae returning.

Choosing between two Indian 12 mg brands? Our Ivecop 12 vs Ivercor 12 comparison covers makers, prices and which weight a 12 mg tablet fits.

Sources

• STROMECTOL (ivermectin) tablets, US prescribing information, revised September 2024: Clinical Pharmacology, Clinical Studies, Indications, Precautions, Adverse Reactions, Dosage and Administration. DailyMed
• US Food and Drug Administration, Drugs@FDA database: ivermectin tablet applications NDA 050742 and ANDAs 204154, 215922, 216808, 216863, 218324, 218509 and 218805, including therapeutic equivalence codes.
• Reis G et al. Effect of early treatment with ivermectin among patients with Covid-19. N Engl J Med 2022;386(18):1721-1731. PMID 35353979.
• Naggie S et al. Effect of ivermectin vs placebo on time to sustained recovery in outpatients with mild to moderate COVID-19. JAMA 2022;328(16):1595-1603. PMID 36269852.
• Naggie S et al. Effect of higher-dose ivermectin for 6 days vs placebo on time to sustained recovery in outpatients with COVID-19. JAMA 2023;329(11):888-897. PMID 36807465.

This article is for information only and is not medical advice. Ivermectin is a prescription medicine in the US. Talk to a doctor about diagnosis and treatment of parasitic infections.