Why do you keep saying two 3 mg chips? My cousin takes four whenever he has a cold.
Knock: an envelope with two chips, not a headline
Highest-stakes line first: two 3 mg chips for a 26-44 kg oncho band is labeled field math. A viral claim is not a second indication on the same stamp.
The knock on this door is a weight band, not a tweet. Someone brings a 3 mg Stromectol blister and a printout that treats the tablet as a general antiviral. Those are two different envelopes. Mix them and you waste a clinic hour.
Onchocerciasis still uses a single oral count aimed at about 150 mcg/kg, taken on an empty stomach with water. In the 26-44 kg row the label writes two 3 mg chips. That is the card I want on the desk first. It is how Merck's Mectizan donation has counted bodies since 1987: kilograms first, tablets second, village third.
Viral claims arrived later, after a 2020 dish paper, and they never inherited that field arithmetic. A glutamate-gated chloride channel in a nematode is not a coronavirus protease. The molecule did not change. The question did.
So this review keeps a pastel-room order. Knock with the two-tablet band. Chart the named parasite trials. Ward-round the scabies second dose and the Loa loa stop. Sign out the COVID platforms as a closed file. If you came for ADME or a full interaction rail, turn to the ivermectin profile instead.
Ward-round: Strongyloides clocks that actually moved
Intestinal Strongyloides stercoralis is the other labeled US job. The Stromectol strongyloidiasis stamp aims near 200 mcg/kg as a single oral dose, empty stomach, water. Some desks repeat that 200 mcg/kg on a second consecutive day. CDC still writes 1-2 days for uncomplicated infection. Follow-up stool two to four weeks later is not optional if larvae were seen.
Marti 1996 is the named comparison I keep on the lilac wall. Three hundred and one children in rural Zanzibar. One 200 mcg/kg ivermectin dose versus albendazole 400 mg daily for three days. Cure 83% versus 45%. Both drugs handled Ascaris. Ivermectin was weak on Trichuris and useless on hookworm. That last pair stops anyone from calling the tablet a general dewormer.
A later Cochrane synthesis (ivermectin versus albendazole or thiabendazole) put parasitological cure higher with ivermectin: risk ratio 1.79 (95% CI 1.55 to 2.08) across 478 participants in four albendazole trials. Adverse events did not separate cleanly. Gann 1994 and later Thai work tested one dose against two. The label still allows a single 200 mcg/kg pass and asks you to prove clearance, not to invent a week-long course because a blog said so.
Hyperinfection is a different room. Immunosuppression, HTLV-1, steroids before a trip to an endemic coast - that is when daily 200 mcg/kg continues until stool and sputum stay negative for two weeks. I do not smuggle that regimen onto a well child with a light stool. And I do not treat a viral tweet as if it were Marti's slide.
The dish that never became a dose
Caly and colleagues (Antiviral Research, 2020) showed SARS-CoV-2 drop in Vero cells at about 5 micromolar ivermectin. That number travelled farther than the paper's own caution. A 5 micromolar bath is not a plasma level after two 3 mg chips, and it is not even a level you can live with after the later 400 mcg/kg COVID protocols.
Labeled 3 mg counts produce nanomolar-range peaks. Most of that is protein-bound. The free concentration that actually meets a cell is lower still. You do not close a 50- to 100-fold gap by 'taking more until the dish comes true.' You hit vomiting, hypotension, confusion, and worse first. Pharmacology is cruel that way, and it is ordinary.
Early outpatient papers then piled up: small, mixed quality, some later retracted, some run where intestinal helminths are common enough that a deworming lift can look like a viral win. Meta-analyses that weighted those papers as if they were Greene or Marti invented a controversy the large platforms later filed.
I do not need a second mechanism lecture here. Glutamate-gated chloride channels in invertebrates explain the parasite rooms. They do not explain a coronavirus ward. The profile already holds that sentence.
Three platform rooms that stayed quiet
| Platform | Dose on the chart | What did not move |
|---|---|---|
| TOGETHER, Brazil, NEJM 2022 | 400 mcg/kg x 3 days | Hospital / long ED composite: 14.7% vs 16.3%, RR 0.90 (0.70-1.16) |
| ACTIV-6, US, JAMA 2022 | 400 mcg/kg x 3 days | Sustained recovery HR 1.07 (0.96-1.17); later 600 mcg/kg x 6 also quiet |
| PRINCIPLE, UK, 2024 | 300-400 mcg/kg x 3 days | Meaningful recovery bar missed; hospital/death OR 1.02, difference 0% |
TOGETHER (Reis, NEJM 2022; NCT04727424) tested 400 mcg/kg daily for three days against placebo in early outpatient Covid-19 in Minas Gerais. In the ivermectin comparison, 100 of 679 (14.7%) hit the composite - hospital admission for progression or an emergency stay longer than six hours - versus 111 of 679 (16.3%) on placebo. Relative risk 0.90 (95% Bayesian credible interval 0.70 to 1.16). Most events were admissions. Superiority never crossed the prespecified bar.
ACTIV-6 (Naggie, JAMA 2022) was a US decentralized platform. Adults 30 and older, mild to moderate disease, ivermectin 400 mcg/kg for three days. Among 1591 who completed, time to sustained recovery (three straight days without symptoms) gave a hazard ratio of 1.07 (95% credible interval 0.96 to 1.17). A later higher-dose ACTIV-6 arm (600 mcg/kg for six days) did not rescue the story. Symptom clocks and worsening composites stayed flat in any way that matters at a desk.
PRINCIPLE (Journal of Infection, 2024) is the UK community platform. Primary analysis: 8811 SARS-CoV-2-positive adults, symptoms up to 14 days, June 2021 to July 2022. Ivermectin 2157, usual care 3256, other arms 3398. Target 300-400 mcg/kg once daily for three days. Time to first self-reported recovery: hazard ratio 1.15 (1.07 to 1.23), median about 2.06 days shorter. The pre-set bar for a meaningful effect (hazard ratio at least 1.2) had posterior probability 0.192. Covid-related hospitalisation or death: odds ratio 1.02 (0.63 to 1.62), estimated difference 0%. Six-month recovery looked alike.
Three rooms. Three designs. One sign-out: this tablet is not an outpatient Covid drug. A cousin who got better after a blister is a person who recovered. It is not a hidden fourth trial.
Loa loa stays on the ward list
The hold that still stops a Mectizan truck is Loa loa. In Central African overlap zones, a person can carry a high blood microfilaria load without a dramatic story. Rapid killing after ivermectin has been followed by encephalopathy, coma, and death. That is not a theoretical box on a label. It is why RAPLOA and local mf counts exist.
Desks usually flag very high loads - often discussed around 20,000 mf/mL and higher still above 30,000 - as the danger band. The Stromectol circular already warns that people with onchocerciasis who are also heavily infected with Loa loa may get serious neurologic events after a microfilaricide. Ivermectin is not the drug of choice for loiasis itself. Diethylcarbamazine (through CDC channels in the US) or a slower albendazole plan sit in that room instead.
On a Dublin ward I still ask the travel line before I cheer a 'just give Stromectol' reflex. West and Central Africa, Calabar swellings, eyeworm stories, eosinophilia that does not match a simple Strongyloides guess - those stall the two-chip count until someone who knows RAPLOA has looked. A mass oncho round without that map is how a good tablet earns a coroner's file.
Mazzotti-type itch, tender nodes, and fever after oncho treatment are expected microfilarial die-off, not Loa encephalopathy. Learn the difference on a quiet afternoon, not at 2 a.m. in a district hospital.
The mite needs a second knock
Four field stamps, four clocks
- Oncho field band: about 150 mcg/kg; 26-44 kg writes two 3 mg chips; adults in nodules persist; rounds repeat.
- Strongyloides labeled pass: about 200 mcg/kg once (some desks, two consecutive days); Marti 83% vs albendazole 45%; prove stool clearance.
- Scabies field habit: 200 mcg/kg, then 7-14 days; SHIFT used that second knock in a whole island group.
- Not on this card: a viral daily stack, a horse paste, or a single mite dose sold as a cure.
Classic scabies is not a US Stromectol indication, and I say that out loud so nobody thinks the oncho band automatically covers a care-home outbreak. Where oral ivermectin is used, the field habit is 200 mcg/kg, then a second knock at seven to fourteen days. Eggs hatch after the first pass. One tablet leaves a nursery.
Romani and the SHIFT group in Fiji (NEJM 2015) put that logic into a community. Mass oral ivermectin at 200 mcg/kg, observed. A second dose of whatever had been given at baseline went out 7-14 days later to people who already had scabies. Permethrin stood in for pregnancy, very small children, and a few other holds. Crusted disease got a tighter ivermectin pair plus permethrin twice a week. Village prevalence fell hard by twelve months.
Later head-to-heads have often given 5% permethrin the edge on cluster cure for ordinary scabies. That does not retire the oral card. It assigns it: outbreaks where cream never reaches every crease, crusted disease as combination therapy, people who cannot coat themselves. The error I keep seeing is a single 12 mg swallow and a shrug. The mite clock is a week, not a mood.
If a reader wants the tablet chemistry or the empty-plate counseling, that is the ivermectin profile. This room only keeps the second-dose chart.
Chart: two chips on a 26-44 kg Mectizan band
1985
Greene NEJM: single-dose ivermectin vs eight-day DEC vs placebo in 30 men with oncho and ocular disease. Safer microfilaricide. Adults untouched.
1987
Mectizan Donation Program starts. Community rounds, height poles, and tablet bands - including two 3 mg chips in the mid-weight row.
1996
Marti AJTMH, rural Zanzibar: 301 children with Strongyloides. One 200 mcg/kg ivermectin dose cured 83%; three days of albendazole 400 mg cured 45%.
2015
Romani SHIFT, Fiji, NEJM: ivermectin mass administration with a second dose at 7-14 days for those who had scabies at baseline. Community prevalence collapsed over a year.
2022-24
TOGETHER, ACTIV-6, then PRINCIPLE close the outpatient COVID question. Hospital doors and meaningful recovery do not move.
Greene's 1985 New England Journal comparison is still the oncho knock I teach. Thirty men with moderate to heavy Onchocerca volvulus and eye involvement got a single oral ivermectin 200 mcg/kg, eight days of diethylcarbamazine, or placebo. DEC lit a harsher systemic reaction and more punctate corneal opacities. Ivermectin dropped skin microfilariae and kept them down at six months. Adult worms in nodules stayed alive. That last line is the one residents skip.
The tablet does not kill the adult Onchocerca. It clears microfilariae and suppresses production for months. That is why mass rounds repeat. The Stromectol oncho table still aims near 150 mcg/kg. Campaigns most often come back at twelve months. An individual patient can be reconsidered as early as three.
Mectizan, Merck's donation name, turned that single-dose microfilaricide into a public-health machine after 1987. The 2015 Nobel to Satoshi Omura and William Campbell named the same field, not a later viral story. When a 32 kg child is counted in a river-blindness round, the US oncho band still writes two 3 mg tablets. Two chips. Not a handful. Not a veterinary syringe.
I keep the 26-44 kg row on a mint card because viral dosing chatter erases it. People hear 'ivermectin' and invent a 12 mg adult ritual for every kilogram. The field program never worked that way. Weight first. Then the count.
Sign-out: keep the bands, file the claim
Keep the two-chip oncho band. Keep the Strongyloides 200 mcg/kg clock. File the antiviral headline with the three platforms.
Sign-out is short. Two 3 mg chips remain the 26-44 kg oncho count. Mectizan still runs on weight bands and a microfilaricide that leaves adult worms in place. Marti's 83% versus 45% still explains why ivermectin, not albendazole, is the Strongyloides first pass. Scabies, where used, needs the second knock. Loa loa still stops a truck.
TOGETHER, ACTIV-6, and PRINCIPLE filed the viral claim. A 5 micromolar dish never became a human dose. Do not let a headline rewrite a field card.
Bring kilograms, travel, Loa risk, and the actual parasite - or the lack of one - to a clinician who can see you before anyone changes a count. This site teaches. It does not dispense.
Last Updated
From the postbag
Questions this study raised
Answered by Dr. Saoirse Byrne, MD · Internal medicine & clinical pharmacology
Readers knock with a two-tablet printout in one hand and a viral thread in the other. These names are editorial. I answer the way I would on a Merrion Square ward-round - numbers first, then the hold.
Because the 26-44 kg onchocerciasis row on the Stromectol stamp is two 3 mg tablets, aimed at about 150 mcg per kilogram, not at a cold. A heavier adult on an oncho or Strongyloides card will count more chips, still from kilograms, still from the labeled table. Four tablets for a viral sniffle is not a field band. It is a habit borrowed from headlines. If your cousin has a documented parasite, his own clinician should set the count from weight and indication. If he does not, extra chips do not become an antiviral just because the blister is in the kitchen.
Mectizan treated millions. Doesn't that prove the drug 'works' for anything?
It proves the drug works as a microfilaricide in onchocerciasis control and as a Strongyloides agent when the stool matches. Greene 1985 and the later community rounds showed skin microfilariae fall and stay down for months. Adult worms remain. That is a specific chart. Millions of safe MDA swallows are a safety story for those indications, not a license to treat a coronavirus. A hammer with a perfect safety record in carpentry still fails as a thermometer.
Marti said 83%. Why would anyone still use albendazole for Strongyloides?
Access, pregnancy questions, and mixed helminth loads. Marti also showed ivermectin was poor on Trichuris and did nothing useful to hookworm, while albendazole cleared hookworm in nearly everyone in that Zanzibar cohort. If the only problem on the slide is S. stercoralis, ivermectin is the first pass I want. If the lab is mixed, the card may need both stories. Cochrane later pooled albendazole comparisons at a cure risk ratio of 1.79 for ivermectin. That is still a nematode result. Bring the stool, not a ranking from social media.
I grew up in a Loa belt. Can I take Stromectol for proven scabies in Dublin?
Not as a casual over-the-counter decision. Heavy Loa loa microfilaremia is the classic reason ivermectin has caused encephalopathy after a mass oncho round. Desks talk in tens of thousands of microfilariae per millilitre. If you have lived in an overlap zone, the right knock is a clinician who will take that history seriously - Calabar swellings, eyeworm, eosinophilia - and who knows when RAPLOA or a blood count is needed before any ivermectin. Proven scabies in Dublin often starts with permethrin anyway. Do not self-dose from a leftover travel blister.
The SHIFT paper used one community dose. Why do you still push a second scabies dose?
SHIFT gave everyone a first observed 200 mcg/kg (or permethrin if they could not take the tablet) and then sent a second dose 7-14 days later to people who already had scabies at baseline. That is the mite clock: eggs hatch after the first pass. Crusted cases got an even tighter pair plus topical permethrin. A single swallow in a family flat is how recurrences get blamed on 'resistance' when the nursery was never treated. Ask your clinician about the second knock if oral therapy is truly the plan.
TOGETHER's 14.7% versus 16.3% looks like a small win. Why do you call it quiet?
Because the interval ran from 0.70 to 1.16 and the trial's own superiority threshold was not met. Most of those events were hospital admissions. A two-point gap that includes 1.0 is how chance looks in a large outpatient composite. ACTIV-6 then failed to shorten sustained recovery in a meaningful way. PRINCIPLE shaved about two days off a self-reported clock but missed its own 'meaningful' hazard-ratio bar and showed a 0% difference on hospitalisation or death. I do not promote a maybe that three platforms declined to sign.
If the lab needed 5 micromolar, why not just take veterinary paste until I get there?
Because you will be toxic long before the dish concentration exists in blood as free drug. Labeled 3 mg counts, and even the 400 mcg/kg COVID protocols, live far below 5 micromolar. Veterinary pastes are concentrated for animals many times a human weight. Overdose looks like vomiting, low blood pressure, confusion, and in bad cases seizures. That is not bravery. It is poisoning. If a human tablet is in the house for a real parasite, talk to a pharmacist or physician. Do not chase a Vero-cell number with horse paste.
Does a second Strongyloides day mean I should take ivermectin for a week 'to be sure'?
No. Some desks repeat 200 mcg/kg on day two for uncomplicated infection. That is still a two-day card, then stool proof at two to four weeks if larvae were seen. A week-long 'just in case' course is how people invent regimens. Hyperinfection on steroids or HTLV-1 is the room where daily dosing continues until samples stay negative for two weeks - and that is a hospital-level decision, not a home experiment. File the extra days unless that room is actually yours.
Where should I read the tablet itself if this page is only the field envelope?
The ivermectin profile holds the labeled counts, empty-plate line, and the holds I will not retell here. This study is the evidence rooms: two chips in the 26-44 kg oncho band, Marti, SHIFT, Loa, and the three platforms. If you want another Oracel study after that, the pain-trial card on Neurontin 800 mg evidence is a different pastel room entirely. Neither page is a prescription.
Read these as teaching on a general point, not as a care plan for whoever asked. Anything specific to you belongs with a prescriber who can see your notes, bloods and full medicine list at once.