Ivermectin 3 mg Tablets: 150 mcg/kg Count Before You Fill

What 150 mcg/kg actually dropped in the onchocerciasis file

The Stromectol label does not open with a theory of parasites. It reports a double-blind, placebo-controlled cut in adults with moderate to severe onchocerciasis. A single oral dose aimed at 150 mcg/kg dropped the geometric mean skin microfilariae count by 83.2% at day 3. At 3 months the same count was down 99.5%. A reduction of more than 90% held for up to 12 months after that one dose.

The evaluation set was 1278 patients. The indication statement cites randomized, double-blind, placebo-controlled and comparative work in 1427 people in West African endemic areas. Some of those studies used diethylcarbamazine citrate as the comparator. The practical take is the dose target. You are counting 3 mg tablets to hit that 150 mcg/kg microfilariae cut, not to kill the adult worm.

The label states the ceiling without a hedge. STROMECTOL has no activity against adult Onchocerca volvulus. Adults live in subcutaneous nodules that are often not palpable. Surgical excision of nodules can still matter because it removes the microfilariae-producing adults. Mass distribution campaigns most often wait 12 months between rounds. For an individual patient, retreatment may be considered as early as 3 months.

WHO still treats communities at least once a year for 10 to 15 years. That span matches the reproductive life of adult O. volvulus under drug pressure. Merck donates the tablets for those programs as Mectizan. None of that program success turns 150 mcg/kg into an antiviral regimen. It is a measured skin-and-eye microfilariae effect with a named adult-worm gap.

Eye findings in the same file need a slower read. Some patients had a rise in anterior-chamber microfilariae at day 3, the way other microfilaricides can. At 3 and 6 months, more ivermectin-treated patients had decreases in that eye count than placebo. The day-3 bump is not the 12-month story. The 12-month story is the skin count staying down.

Where a 3 mg x 20 carton is actually filled

The ledger below lists licensed US pharmacies that already show up on coupon and cash lists for human 3 mg ivermectin. Twenty tablets is the carton GoodRx prices as a unit. It is not a 150 mcg/kg math shortcut. A 70 kg onchocerciasis count is still four 3 mg tablets, not the whole box.

Each name opens that chain's own pharmacy page. Coupon dollars sit in the caption, because a GoodRx or SingleCare number is not a Kroger shelf sticker. Gravix sells nothing. A clinician still has to write the 3 mg count for a labeled parasite, not for a virus.

The other labeled cut: 200 mcg/kg for intestinal strongyloidiasis

Intestinal Strongyloides stercoralis is the second US tablet indication. The target is a single oral dose of about 200 mcg/kg, not 150. The tablet table changes with that target. 15-24 kg takes one 3 mg tablet. 25-35 kg takes two. 36-50 kg takes three. 51-65 kg takes four. 66-79 kg takes five. At 80 kg and above the label says 200 mcg/kg.

Cure in the clinical-studies section meant no larvae in at least two follow-up stools 3 to 4 weeks after therapy. Against albendazole 200 mg twice daily for 3 days, a single 170-200 mcg/kg ivermectin dose cured 24 of 26 (92%) in one international comparison. A WHO study using the same ivermectin cut cured 126 of 152 (83%). Albendazole cured 55% and 45% in those same rows.

Thiabendazole 25 mg/kg twice daily for 3 days was the other comparator. A single 200 mcg/kg ivermectin day looked similar: 9 of 14 (64%) versus 13 of 15 (87%) in one international comparison. The US studies were 14 of 14 versus 16 of 17. The indication text summarizes the single 200 mcg/kg cure range as 64-100%.

A France study in a non-endemic setting, so reinfection was unlikely, found larvae back in stool as late as 106 days after ivermectin. The label's practical take is follow-up, not a shrug. Do at least three stool examinations over the three months after treatment. Use a concentration method such as a Baermann apparatus. If larvae return, retreat.

Activity against S. stercoralis is limited to the intestinal stages. Disseminated disease is not the studied indication. In immunocompromised patients, including people with HIV, repeated courses may be needed and cure may not be achievable. The label mentions treatments at 2-week intervals and, for extra-intestinal control, possible monthly suppression. That regimen was not pinned down in an adequate controlled study.

How the 3 mg tablet table is meant to be used

Each Stromectol tablet is 3 mg. The onchocerciasis table starts at 15 kg. One tablet covers 15-25 kg. Two cover 26-44 kg. Three cover 45-64 kg. Four cover 65-84 kg. At 85 kg and above the label leaves the count and says 150 mcg/kg.

That is why a headline that says "take ivermectin" without a weight is not a dose. A 70 kg adult on the onchocerciasis line takes four 3 mg tablets, 12 mg, as a single oral dose. A 90 kg adult is not automatically five tablets. The label switches to a calculated 150 mcg/kg once weight clears 85 kg.

Children under 15 kg are outside the established pediatric safety line on the US tablet label. Safety and effectiveness have not been established below that weight. Do not invent a half-tablet rule from a farm-store tube. The human 3 mg tablet exists so the count can match the table.

The same tablet is swallowed on an empty stomach with water for the labeled uses. That instruction sits in both the onchocerciasis and strongyloidiasis dosing sections. It also sits in the patient information. A high-fat meal is a different experiment, covered later, and it is not how the labeled parasite doses are written.

Generic 3 mg tablets are the usual US pharmacy fill. Stromectol is the branded name on the DailyMed file most people still quote. Either way the count is the same if the tablet is 3 mg. Confirm the strength on the bottle before you multiply tablets.

The 12 mg fasting peaks and the 2.5-fold food jump

Two fasting studies gave a single 12 mg dose, a mean of 165 mcg/kg, to healthy volunteers. Mean peak H2B1a was 46.6 ng/mL in one study (range 16.4-101.1). The other study peaked at 30.6 ng/mL (range 13.9-68.4). Both peaks sat at about 4 hours. Plasma levels track dose in a roughly proportional way.

The plasma half-life after an oral dose is about 18 hours. Drug and metabolites leave almost entirely in feces over an estimated 12 days. Less than 1% of the dose shows up in urine. That is why a kidney number is not the first adjustment people reach for, and why a stool follow-up still matters more than a blood level in strongyloidiasis.

A separate multiple-dose study pushed 30-120 mg (333-2000 mcg/kg) fasted, and 30 mg after a standard high-fat meal with 48.6 g of fat. Thirty milligrams after that meal raised bioavailability about 2.5-fold versus 30 mg fasted. The labeled parasite directions still say empty stomach with water. Scabies clinicians sometimes flip that on purpose. That is an off-label food choice, not the Stromectol parasite line.

In vitro, CYP3A4 does most of the hepatic work. CYP2D6 and CYP2E1 show up to a smaller extent depending on the method. At clinically relevant concentrations, ivermectin did not meaningfully inhibit CYP3A4, CYP2D6, CYP2C9, CYP1A2, or CYP2E1 in human liver microsomes. The drug-interaction file is still thin. Post-marketing reports have rarely noted a higher INR when ivermectin was given with warfarin.

Neurotoxicity is in the warnings now: somnolence, stupor, coma, confusion, disorientation, and death have been reported, including in people without onchocerciasis and without Loa loa. Those events generally eased with supportive care and stopping the drug. That is a safety sentence, not a reason to dose a virus.

TOGETHER and ACTIV-6: no clinical benefit for COVID-19

COVID-19 is not a labeled use. The FDA has not authorized or approved ivermectin to treat or prevent COVID-19 in people or animals. That is a regulatory fact, not a soft preference. Large randomized trials then measured the clinical question and came back empty.

TOGETHER, reported in the New England Journal of Medicine in 2022, randomized symptomatic SARS-CoV-2-positive adults in Minas Gerais, Brazil. The ivermectin arm used 400 mcg/kg once daily for 3 days versus placebo. Patients had symptoms for up to 7 days and at least one risk factor for progression. Of 3515 assigned across platform arms, 679 received ivermectin and 679 received the matched placebo.

The primary composite was hospitalization for COVID-19 within 28 days or an emergency-department stay longer than 6 hours for worsening. In the intention-to-treat set, 100 patients (14.7%) on ivermectin met that composite versus 111 (16.3%) on placebo. Relative risk 0.90, 95% Bayesian credible interval 0.70 to 1.16. Most events were hospital admissions: 171 of 211. Secondary outcomes did not move either.

ACTIV-6 tested the same idea in US outpatients. One arm used 400 mcg/kg daily for 3 days and found no clinically meaningful gain in symptom resolution, hospitalization, or emergency visits. A later arm pushed a targeted maximum of 600 mcg/kg daily for 6 days in 1206 adults with mild to moderate COVID-19. Time to sustained recovery, defined as 3 straight days without symptoms, did not improve versus placebo. The composite of hospitalization, death, or urgent care by day 28 did not improve (hazard ratio 1.0, 0.6-1.5).

A dish assay is not those endpoints. TOGETHER and ACTIV-6 already used doses above the labeled 150-200 mcg/kg parasite cuts and still did not show a clinical benefit. Ivermectin remains a parasite tablet. It is not a COVID medicine. The longer argument lives on the claims that outran the file.

Scabies at 200 mcg/kg is a protocol, not a tablet indication

Oral ivermectin is not FDA-approved for scabies. CDC still publishes a classic-scabies regimen that many US clinicians use: 200 mcg/kg per dose, two doses 7 to 14 days apart, taken with food. The food line is the opposite of the Stromectol empty-stomach instruction. CDC says scabies experts want the extra bioavailability.

The second dose is there because a single oral dose is a weak egg drug. Mites that hatch after the first swallow are the reason for the 7-14 day repeat. Crusted scabies is a different schedule. CDC lists multi-dose ivermectin plus a topical, with example calendars of 3, 5, or 7 oral doses depending on severity. There is no single consensus calendar.

Household timing matters as much as milligrams. Treat close contacts on the same days when the clinician says the cluster is shared. Wash or bag bedding and clothes. Oral tablets do not clean a sofa. If someone cannot apply permethrin from neck to toes twice, the oral option is often why a household finishes the job.

Safety limits travel with the off-label use. CDC repeats the tablet label's gaps: children under 15 kg and pregnant people do not have established oral-ivermectin safety. Do not stretch a 3 mg count into those groups because a school outbreak is inconvenient.

Compare that honesty with COVID headlines and the difference is the endpoint. Scabies protocols at least name a mite, a mcg/kg figure, and a repeat window. COVID use had large RCTs and no clinical benefit. If you want the parasite-versus-virus split in one place, start with uses and evidence and the antiparasitic comparison.

What the molecule binds, and which stages it misses

Avermectins bind glutamate-gated chloride channels in invertebrate nerve and muscle. Chloride rushes in. The cell hyperpolarizes. The parasite is paralyzed and dies. The class can also touch other ligand-gated chloride channels, including GABA-gated ones. That is the microbiology section, not a slogan.

Selectivity has two stated reasons. Some mammals do not have glutamate-gated chloride channels. Avermectins also have low affinity for mammalian ligand-gated chloride channels. Ivermectin does not readily cross the human blood-brain barrier. Those sentences are why a labeled 3 mg count can be used in people while still wrecking a nematode's motor plate.

Life-cycle gaps matter as much as the channel. Ivermectin is active against various stages of many, not all, nematodes. For Onchocerca it hits tissue microfilariae and not the adult. For Strongyloides it hits intestinal stages. If you expected a single swallow to sterilize every form of every worm, the label already told you no.

Chemistry on the same page is a mixture, not a single structure. At least 90% is 22,23-dihydroavermectin B1a (H2B1a). Less than 10% is B1b. Molecular weights are 875.10 and 861.07. The powder is white to yellowish-white, melts around 155 C, and does not dissolve in water. The 3 mg tablet adds cellulose, starch, magnesium stearate, BHA, and anhydrous citric acid.

Topical products are different approvals. Ivermectin cream (Soolantra) is a rosacea product. Ivermectin lotion (Sklice) is a head-lice product. Neither is a substitute for a counted 3 mg oral dose, and the oral tablet is not those leave-on products. Keep the formulation attached to the indication.

Mazzotti numbers, Loa loa, pregnancy, and the 15 kg floor

Onchocerciasis reactions are often the dying microfilariae, not a simple drug rash. In 963 adults given 100-200 mcg/kg, Mazzotti-type worsening showed up in the first 4 days. Pruritus hit 27.5%. Skin edema or rash hit 22.7%. Fever hit 22.6%. Inguinal node tenderness hit 13.9% and enlargement 12.6%. Axillary enlargement was 11.0%. Arthralgia or synovitis was 9.3%.

Drug-related facial edema, peripheral edema, orthostatic hypotension, and tachycardia sat in the 1-3.5% range in that same adult set. Headache and myalgia were the most common events overall, 22.3% and 19.7%, regardless of causality. Severe postural hypotension has been treated with fluids, lying flat, saline, and sometimes parenteral corticosteroids. Milder cases have been treated with antihistamines or aspirin. Those treatments were not settled in controlled Mazzotti trials.

Loa loa is the travel question that can turn fatal. People with onchocerciasis who also carry a heavy Loa loa load have developed encephalopathy, sometimes fatal, after an effective microfilaricide. Pain, red eye, conjunctival hemorrhage, incontinence, inability to stand, seizures, and coma sit on that list. If exposure to Loa-endemic West or Central Africa is real, assess for loiasis before you dose and watch afterward.

Sowda (hyperreactive onchodermatitis) can react more severely after a microfilaricide, especially with edema and a worse rash. Strongyloidiasis patients should not be handed the onchocerciasis eye-and-Mazzotti script as if it were their risk set. The label says those reactions would not be expected in strongyloidiasis.

Pregnancy: animal teratogenicity (cleft palate; clubbed forepaws in rabbits) appeared 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. Milk contains low concentrations. Treat a nursing mother only if delay is worse than the possible risk to the newborn. Under 15 kg, the pediatric line is not established. Over 65 years, the trials did not enroll enough people to split the response.

A pharmacy 3 mg fill is not livestock paste

US 3 mg tablets are a prescription product. Telehealth shops and coupon sites will show Stromectol or generic ivermectin next to Walgreens and other chains. A live prescription still has to sit behind the fill. Price shopping is fine. Skipping the diagnosis is not.

Veterinary pastes, pour-ons, and injectables are approved for animals at animal concentrations. The FDA has warned people not to take those products for COVID-19. The human 3 mg tablet is the dose unit the onchocerciasis and strongyloidiasis tables assume. A horse tube is not a weight calculator.

If the job is pinworm in a household, ivermectin is usually the wrong first reach. That is a mebendazole 100 mg chewable problem, with a planned 2-3 week repeat. Read how to take mebendazole for pinworm and roundworm before you borrow this tablet.

If the job is river blindness or intestinal Strongyloides, count the 3 mg tablets to the matching mcg/kg line. Empty stomach, water, then the follow-up the indication requires. Onchocerciasis needs retreatment because adults survive. Strongyloidiasis needs stools because larvae can return weeks later.

Do not stretch those two labeled cuts into a respiratory virus. TOGETHER and ACTIV-6 already ran that experiment. They measured hospital time, recovery, and urgent care. They did not find a clinical benefit. The FDA has not approved that use.