The organism named on the tablet description
The DailyMed Stromectol description (setid 681888c9-af79-4b7d-ae80-c3f4f6f1effd, revised September 2024) calls Stromectol a semisynthetic anthelmintic. Ivermectin is derived from the avermectins, isolated from fermentation products of Streptomyces avermitilis.
The public record of that isolation sits with Satoshi Omura and the Kitasato Institute in Japan, who found the producing strain in a soil sample. William Campbell and colleagues at Merck showed that the fermentation products could clear parasites in animals. Those two lines of work are what the 2015 Nobel Prize in Physiology or Medicine cited for Campbell and Omura: discoveries concerning a novel therapy against infections caused by roundworm parasites. The same year's prize also recognized Tu Youyou for artemisinin. The prize is a history of the discovery. It does not add an indication.
Ivermectin the substance is a white to yellowish-white crystalline powder, melting point about 155 C, insoluble in water, freely soluble in methanol. The tablet is a different object from the powder: 3 mg of ivermectin plus microcrystalline cellulose, pregelatinized starch, magnesium stearate, butylated hydroxyanisole, and anhydrous citric acid.
Why the human drug is a dihydro mixture
Ivermectin is not the raw fermentation broth poured into a bottle. It is a mixture containing at least 90% 5-O-demethyl-22,23-dihydroavermectin A1a and less than 10% of the related 25-de(1-methylpropyl)-25-(1-methylethyl) analogue. Everyday names for that pair are 22,23-dihydroavermectin B1a and B1b. Formulas are C48H74O14 and C47H72O14. Molecular weights are 875.10 and 861.07.
The hydrogenation step, saturating the 22,23 bond, is the chemical difference between the leading avermectin fermentation components and the substance in the tablet. Weight charts came later. They count 3 mg tablets.
Selectivity, as the microbiology section explains it, comes from glutamate-gated chloride channels on invertebrate nerve and muscle. The drug binds those channels, chloride floods in, the cell hyperpolarizes, and the parasite is paralyzed and dies. Some mammals lack those glutamate-gated channels. Avermectins also have low affinity for mammalian ligand-gated chloride channels, and ivermectin does not readily cross the human blood-brain barrier. Reported neurotoxicity, including after exposure to veterinary formulations, still occurs. The barrier sentence does not authorize an animal product or extra tablets. The exposure list is on the weight guide.
Mectizan, and the 12-month campaign interval
A Japanese soil sample yields Streptomyces avermitilis. Merck's parasitology group finds animal activity in the fermentation products.
Merck opens the Mectizan Donation Program for onchocerciasis in endemic communities.
Stromectol 3 mg tablets, NDA 050742, marketing start 22 November. Distributor: Merck Sharp and Dohme.
Nobel Prize in Physiology or Medicine to Campbell and Omura for a roundworm therapy, shared that year with Tu Youyou.
Mectizan is the name used for ivermectin in Merck's donation program. In 1987 the company said it would supply the drug for onchocerciasis, river blindness, for as long as it was needed in endemic communities. Village rounds in that program are a public-health supply. They do not publish a US copay this page could honestly repeat.
The Stromectol onchocerciasis dosage text still carries the operational trace of those rounds. In mass distribution campaigns the most common dose interval is 12 months. For a single patient, retreatment may be considered as soon as 3 months. The dose those programs are built around is about 150 mcg/kg, aimed at microfilariae. Adult Onchocerca worms survive in nodules.
Strongyloidiasis traveled a separate clinical path from the blindness campaigns: about 200 mcg/kg once for intestinal infection, then stool exams. Same molecule, different organism, different interval. The two charts are compared on the parasite guide. Trial cells, including the ones that did not all point the same direction, are on the evidence review.
The US tablet dated 22 November 1996
NDA 050742 lists a marketing start date of 22 November 1996. The packager on the current listing is Merck Sharp and Dohme LLC, Rahway, New Jersey. How-supplied text describes white, round, flat, bevel-edged 3 mg tablets coded MSD on one side and 32 on the other, in unit-dose packages of 20.
Two NDC codes appear: 0006-0032-20, with a package marketing start of 22 November 1996, and 0006-0032-01, with a package marketing start of 20 September 2024. The later code is another 20-tablet package on the same application, still 3 mg. Each package is two blister strips of 10. The foil strip is not child-resistant. Bulk packs are not meant to be handed out as-is. Tablets are moved into a proper container. Store below 30 C (86 F).
There is no 6 mg or 12 mg Stromectol oral tablet on this listing. When a calculated dose is larger than 3 mg, the count is several 3 mg tablets. That arithmetic is the weight guide's job. Manufacturing notes on the package say the tablet is made for Merck Sharp and Dohme, with ivermectin as the active ingredient.
Names that get swapped after the Nobel
Four names sit on one molecule and cause most of the mix-ups. Ivermectin is the substance. Stromectol is the US brand of the 3 mg tablet. Mectizan is the donation-program name tied to onchocerciasis campaigns since 1987. Streptomyces avermitilis is the organism named in the description.
A livestock product that says ivermectin on the tube is a fifth object. It shares a word with the tablet and not the formulation, the strength, or the instructions. Accidental human exposures are filed under overdosage.
The Nobel line is sometimes used as a shopping slogan. Campbell and Omura were recognized for work that led to a treatment for roundworm infections. The US indications that followed are intestinal strongyloidiasis and onchocerciasis. COVID-19 is not one of them. A history of a soil organism does not create a virus dose.
Someone who needs a US fill after reading the dates still needs a prescription and a pharmacy licensed in their state. That path is the compound page, read with the FDA guide to buying medicines safely from an online pharmacy. This history does not quote a price, a coupon, or a no-prescription offer.
Questions people ask next
Is Mectizan a different drug from Stromectol? Mectizan is the name used in the donation program for onchocerciasis. Stromectol is the US brand of ivermectin 3 mg tablets. Same active ingredient, different channel.
When did the US tablet start? Marketing start for NDA 050742 is 22 November 1996. A second NDC, 0006-0032-01, shows a package date of 20 September 2024. That is packaging, not a new strength.
What should the tablet look like? White, round, flat, bevel-edged, MSD on one side and 32 on the other. Packages of 20. Foil is not child-resistant. Store below 30 C.
Who received the 2015 Nobel? William Campbell and Satoshi Omura, for discoveries leading to a therapy against roundworm infections. Tu Youyou shared the 2015 prize for artemisinin.
Does the donation program set a US price? No price is stated here. Mectizan rounds were a public-health supply for endemic onchocerciasis. A US prescription fill is a different transaction, described on the compound page.
Does the origin story add COVID? No. The organism, the dihydro mixture, the 1987 program, and the 1996 tablet all sit with the worm uses. There is no virus indication in that sequence.