I weigh about 78 kg. How many 3 mg tablets is an onchocerciasis pass?
Chip math is not the mcg/kg
Prescribers think in micrograms per kilogram. Cabinets dispense 3 mg tablets. The working card exists because those two languages drift apart the moment someone eyeballs a blister.
Stromectol in the United States is a 3 mg oral tablet. There is no licensed 6 mg or 12 mg human chip on the current label this desk files. Onchocerciasis dosing is a single oral dose designed to provide approximately 150 mcg of ivermectin per kilogram. Strongyloidiasis uses approximately 200 mcg/kg. Both indications tell the patient to take tablets on an empty stomach with water. If you only remember one number from a social post, you will order the wrong stack. A 70 kg adult on the river band is not the same chip count as a 70 kg adult on the gut-worm band.
The card's ping is the chip. The trace is the official weight table, not a back-of-envelope 'one tablet per 15 kg' chant that people steal from the 200 mcg/kg world and apply to onchocerciasis. Flag any instruction that starts from a veterinary syringe or a paste line. Post the human table. Edinburgh will not invent a tablet strength the label does not list. If a clinic outside the US uses a different scored product, that is their monograph, not this card.
Onchocerciasis bands on a 3 mg tablet
| Body weight | Onchocerciasis 3 mg count (150 mcg/kg) | Strongyloides 3 mg count (200 mcg/kg) |
|---|---|---|
| 15-25 kg | 1 tablet (15-25) | 1 tablet only if 15-24; 2 if 25 |
| 26-35 kg | 2 tablets | 2 tablets (25-35) |
| 36-44 kg | 2 tablets | 3 tablets (36-50) |
| 45-50 kg | 3 tablets | 3 tablets |
| 51-64 kg | 3 tablets | 4 tablets (51-65) |
| 65-79 kg | 4 tablets (65-84) | 5 tablets (66-79) |
| 80-84 kg | 4 tablets | Calculate 200 mcg/kg |
| >=85 kg | Calculate 150 mcg/kg | Calculate 200 mcg/kg |
Label Table 2 is the river card. Body weight 15 to 25 kg: one 3 mg tablet. 26 to 44 kg: two. 45 to 64 kg: three. 65 to 84 kg: four. At 85 kg and above, calculate 150 mcg/kg rather than pretending the top band still fits a neat chip count. Those bands are how a programme hands a saucer of tablets to a queue without doing long division in the dust. They are also how a UK or US clinic, facing a traveller or a migrant with a documented Onchocerca file, turns a weight into an order.
Do not import Table 1 by habit. Strongyloidiasis bands run 15-24 kg one tablet, 25-35 two, 36-50 three, 51-65 four, 66-79 five, and at 80 kg and above 200 mcg/kg. The breakpoints differ because the mcg/kg target differs. A person who 'always takes four' for a previous strongyloides pass may be over or under on an onchocerciasis pass. This is the most common arithmetic error I see when a well-meaning relative forwards a screenshot. Order the band that matches the parasite name, then stop.
Water, empty gut, no 2.5-fold fat lift
The label's patient line is short: empty stomach, water. Pharmacokinetics explain why the card is stubborn about it. After single 12 mg fasting doses in healthy volunteers - a mean of about 165 mcg/kg - peak plasma of the major component landed near 4 hours, with wide ranges. Terminal half-life is about 18 hours. Almost all of the dose leaves in faeces over roughly 12 days; less than 1 percent in urine. A multiple-dose study then gave 30 mg after a standard high-fat meal (48.6 g of fat) and saw about a 2.5-fold increase in bioavailability versus the same 30 mg fasted.
Programmes and the US label chose the fasting exposure. Chasing the fat lift to 'make it stronger' is not the onchocerciasis card. It is a way to wander off the studied 150 mcg/kg pass and toward central-nervous-system exposure you did not ask for. CYP3A4 is the main metabolic route; CYP2D6 and CYP2E1 showed up as minor in vitro players. Rare post-marketing INR rises with warfarin are a check-the-INR note, not a reason to skip a needed river pass. Take the chips with water, no breakfast, no 'just a bit of toast to settle the stomach' unless the prescriber has rewritten the card for a named reason.
Twelve-month MDA versus a clinic 3-month pass
Mass campaigns most often come back at 12 months. A named patient in clinic may be retreated at intervals as short as 3 months.
Those two clocks sit on the same label paragraph. They are not a contradiction. MDA is a transmission tool: crash community microfilariae once a year, keep blackflies biting people who are not shedding, come back before the nodules restock the skin. A clinic clock is a symptom and load tool: a traveller, a residual focus, a person with ugly skin or eye disease may need a tighter interval. CDC's care note adds a useful negative: there is no evidence that prolonged daily treatment beats the annual pass for onchocerciasis, because one dose already drops the load for a year or more.
Some trial communities in Ghana saw better sustained skin clearance with semiannual ivermectin than annual, with or without albendazole. That is a programme-frequency signal, not a new home schedule you invent after watching a video. You do not add a daily 3 mg habit 'to be sure'. You pick a calendar that a ministry or a specialist has actually chosen, then you count chips to the band. If the person in front of you has no Onchocerca diagnosis, this card closes. Strongyloides, scabies, and other off-label mite or louse uses are different cards with different repeats. They do not inherit the river calendar.
Adults keep seeding; plan the next count
Write this on the card in ink: STROMECTOL has no activity against adult Onchocerca volvulus. The adults live in nodules that are only sometimes palpable. Nodulectomy can remove a factory; it does not scale to a river valley. Ivermectin knocks down the larvae in skin and eye and can suppress embryogenesis for a stretch, which is why a year of low counts is real and why a single lifetime dose is a fantasy. The patient-information line on the label is the one I want copied into after-visit notes: treatment does not kill the adult parasites, so follow-up and retreatment are usually required.
That is the operational meaning of the trial file's 99.5 percent month-3 drop. The skin is quiet. The nodules are not retired. Plan the next count - a year in MDA, sooner in clinic - the same day you order the first 3 mg stack. If someone wants a drug that aims at adults, that is a specialist conversation about doxycycline and Wolbachia, not a second box of Stromectol taken daily. This card will not smuggle an adulticide claim into a chip count.
Loa loa blood before the first chip
West or Central African exposure is a stop-the-queue item. Heavy Loa loa microfilaraemia plus a microfilaricide can produce a serious or fatal encephalopathy - neck and back pain, red eye, conjunctival haemorrhage, incontinence, collapse of gait, confusion, seizures, coma. The syndrome is rare after ivermectin and it is real enough that programmes in co-endemic zones screen. The label's instruction is pretreatment assessment for loiasis and careful post-treatment follow-up when the exposure is significant. A working card that skips the travel history is a bad card.
Edinburgh sees this as a history question, not as a tropical-medicine party trick. 'I lived in Cameroon' or 'I took a research post in Gabon' changes the first step. It does not automatically forbid the 3 mg onchocerciasis pass. It moves the pass to a service that can quantify Loa loa and watch the patient. Sowda - hyperreactive onchodermatitis - is a second phenotype flag: more oedema, uglier skin flare. Neither flag is a viral-paste story. Both belong above the chip count on the card.
Pruritus 27.5 percent is a Mazzotti flag
Expect itch, rash, fever, and tender nodes in a meaningful minority when skin is heavily loaded. The 963-adult trial list is the card's reference: pruritus 27.5 percent, fever 22.6 percent, skin involvement 22.7 percent, inguinal tenderness 13.9 percent, in the first four days. Mild to moderate historical management was antihistamine and/or aspirin. Postural hypotension got oral fluids, lying flat, saline, sometimes parenteral corticosteroid. That is supportive care for a dying-larva storm, not an antidote shortage.
Ocular symptoms - foreign-body sensation, lid oedema, uveitis, limbitis, keratitis - can come from the disease and from treatment. They were rarely tied to vision loss in the trial programme and often settled without steroid. Still, a person with known eye involvement needs a real follow-up plan, not a 'you'll be fine' text. Strongyloidiasis patients should not be talked into expecting a Mazzotti; the label says those reactions belong to onchocerciasis. If the indication on the card is gut Strongyloides, file a different side-effect list: dizziness and itch around 3 percent, a little nausea and diarrhoea, the odd bit of fatigue.
Holds: pregnancy, under 15 kg, paste
| Card line | Onchocerciasis pass | Do not do |
|---|---|---|
| Target | About 150 mcg/kg as 3 mg chips | Borrow 200 mcg/kg from strongyloides |
| Food | Empty stomach, water | Chase a high-fat 2.5x lift |
| Clock | 12-month MDA; clinic >=3 months | Invent a daily 3 mg habit |
| Adults | Still alive in nodules | Call one pass a cure |
| Loa loa | Screen if West/Central Africa | Dose first, ask later |
| Paste | Never | Convert a horse syringe to chips |
Pregnancy: animal teratogenicity (cleft palate; clubbed forepaws in rabbits) showed up at or near maternotoxic doses. There are no adequate well-controlled studies in pregnant women. The label says ivermectin should not be used during pregnancy because safety has not been established. Breast milk carries low concentrations; treat a nursing mother only when delay is worse for her than the possible risk to the infant. Under 15 kg: safety and effectiveness not established. Over 65: trials did not enrol enough older adults to prove a different response; start from the same band and remember comorbidity. Hypersensitivity to any component is the only listed contraindication.
Paste is not a hold. Paste is a refusal. Veterinary ivermectin is built for animals that weigh hundreds of kilograms. Concentration, excipients, and the absence of a 3 mg onchocerciasis band make farm products a toxicology case, not a thrift option. Neurotoxicity - somnolence, stupor, coma, confusion - has been reported even without Loa loa, generally easing when the drug is stopped and support is given. Immunocompromised strongyloides is a different hold pattern: repeats at about two weeks, possible monthly suppression, cure not promised. Do not copy that pattern onto a river-blindness card. And do not copy a river card onto a viral illness. The trial file already posted those negatives.
Where the sibling files sit on this desk
This card orders chips. It does not retell Kawana, and it does not reprint the 83.2 and 99.5 percent drops except as a reason the calendar is yearly. For the soil ping, open the discovery history. For Liberia rungs, DailyMed curves, and the empty viral endpoints, open the trial-signal journal. For glutamate-gated chloride channels, CYP3A4, and the full interaction list, stay on the ivermectin monograph. Three genres, three jobs. If you catch this page sliding into a mechanism lecture, it has failed the card.
Ping the 3 mg object. Trace the band that matches onchocerciasis. Flag Loa loa, pregnancy, under-15 kg, fat, paste, and any daily-habit invention. Post a counted pass with a next date. That is the method. It is also the limit. I have not examined you. A traveller's eosinophilia, a skin snip from a focus, a leftover blister from a relative's strongyloides treatment - those are clinic objects. Bring them to a person who can write a real order. This Edinburgh working card is teaching. It is not a pharmacy counter and it is not a private prescription.
Reader mail
Reader questions on this article
Answered by Dr. Julian Osei, MD · Internal medicine & infectious disease
Working-card mail from named readers. I count chips and name holds. I do not write a personal order from this desk.
On the US Stromectol river table you sit in the 65 to 84 kg band, which is four 3 mg tablets for a single onchocerciasis pass aimed at about 150 mcg/kg. If someone instead uses the strongyloidiasis table on you, 66 to 79 kg is five tablets because that indication aims at about 200 mcg/kg. Same body, different parasite, different stack. I will not bless a fifth tablet 'just to be sure' for river blindness. I also will not bless a kitchen scale substitution if your weight is a guess. Weigh, pick the indication, read the matching band, take the chips fasting with water. If you are 85 kg or more, the river table stops being a neat chip count and becomes a 150 mcg/kg calculation.
Why can't I take the tablets with dinner so I don't feel sick?
Because the labelled onchocerciasis exposure was built fasting, and a high-fat meal can raise bioavailability about two and a half times. That is not a friendly cushion. It is a different dose. Empty stomach and water keep you on the 150 mcg/kg pass the West Africa carton studied. If nausea is the fear, it is still usually milder than people expect, and it is not a reason to add chips of butter. A clinician who is treating a stubborn off-label infestation sometimes uses food on purpose. That is a rewritten card, not a default. For river blindness I want the boring version: wake, water, swallow the counted 3 mg stack, eat later.
The campaign in my parents' district comes once a year. My cousin's clinic said three months. Who is right?
Both can be, because the label prints both clocks. Mass distribution most often uses 12 months. That is a transmission clock for a whole community. A clinic treating an individual may retreat as soon as 3 months if skin or eye disease and a remaining load say so. Neither clock is a daily tablet. CDC's note is useful here: one dose already suppresses microfilariae for a year or more, so inventing a prolonged daily course does not have evidence behind it. If your cousin has a named specialist and a documented Onchocerca load, a 3-month clinic pass can be the tighter tool. If the district is running MDA, annual is the machine. Do not mix the two calendars in one blister pack without a person who owns the file.
I took four tablets last year for a worm in my gut. Same four this year for river blindness?
Not automatically. Last year's four may have been a strongyloidiasis count at 200 mcg/kg. This year's onchocerciasis count at 150 mcg/kg uses different weight breakpoints. At some weights the chip number matches; at others it does not. I have seen people reuse a five-tablet strongyloides stack for a river pass and call it loyalty to 'what worked'. What worked was a different target. Tell the prescriber the old indication and the old count, then let them read Table 2, not your memory. And if last year's 'worm' was never speciated, stop. This card does not treat a family story. It treats Onchocerca volvulus or it stays in the drawer.
I spent two years in Gabon. Does that change the first tablet?
It changes the first question. Gabon sits in Loa loa country. If you now need ivermectin for onchocerciasis - or for any other labelled or off-label reason - the card says assess for loiasis before the microfilaricide, then watch you after. A heavy Loa loa load plus a sudden larval die-off is the encephalopathy scenario the label describes. Rare, ugly, preventable by not being casual. I do not tell every Edinburgh patient to get a Loa smear. I do tell anyone with significant West or Central African time to put that sentence at the top of the consult, not in a footnote after the chips are swallowed. Screening is a delay of days. Encephalopathy is not a delay you can walk back.
Is the itch after the dose a reason to skip next year's campaign?
Usually no. On an onchocerciasis card, itch, rash, fever, and sore groin nodes in the first days are the Mazzotti pattern from dying microfilariae. About a quarter of trial adults itched. About a fifth ran a fever or a skin flare. That is miserable and it is also the drug hitting the target. Mild cases were handled with antihistamine or aspirin in the older practice notes. Feeling wrung out for a couple of days is not, by itself, a lifetime exemption from MDA. What is a reason to pull you out of a queue is a prior neurologic event, a known heavy Loa loa load, pregnancy, a child under 15 kg, or a past hypersensitivity to a component. Bring the itch to the campaign nurse or your clinician. Do not retire yourself from a river programme on a forum's advice.
Can I split adult tablets for my 12 kg child?
Not from this card. Safety and effectiveness below 15 kg have not been established. A 12 kg child is under that line. Splitting a 3 mg chip to invent a baby dose is not 'being careful'. It is leaving the evidence. Programme height sticks and paediatric policies exist because the open childhood file starts at 6 years and 17 kg in the study the label quotes, not at a toddler's snack time. If a paediatric infectious-disease service has a named indication and a protocol, that is their card. Mine stops at 15 kg. I will also not convert a veterinary paste into a paediatric millilitre. That is how emergency departments meet this molecule.
I'm trying to conceive. Is a leftover 3 mg strip a problem?
The label is conservative: do not use in pregnancy because human safety is not established, and animal studies showed cleft palate and, in rabbits, clubbed forepaws at or near doses that already harmed the mother. A leftover strip from a relative's strongyloides treatment is not a pre-conception vitamin. If you are already pregnant and you have a serious parasitic infection, that is a specialist risk-benefit conversation, not a working-card default. If you are planning, park the blister and ask before anyone counts chips. Breastfeeding is a separate, softer line - low milk levels, treat only if delay is worse for the mother. I will not give you a wink and a 'one tablet won't matter'. The card either has a named indication and a yes, or it stays shut.
Where does chip math stop and the other journal pages start?
Chip math stops when you start asking who found the bacterium, or what percent the skin snip fell on day 3, or how glutamate-gated chloride channels work. Those are the history, the trial file, and the monograph. This page should leave you able to say: onchocerciasis, 150 mcg/kg, these 3 mg bands, fasting water, yearly versus three-month clocks, adults still alive, Loa loa screen, pregnancy and under-15 kg holds, no paste. If a sentence on this card could be swapped onto a metformin page, I wrote it badly. If it could be swapped onto the ivermectin monograph's 'what it is' section, I also wrote it badly. Different genre. Same molecule. Your clinician still has to sign the real order.
General education from a clinician, not personal medical advice. Bring your own history to your own prescriber.
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