Ivermectin is dosed by body weight, not as a fixed tablet count. Every standard regimen is expressed in micrograms per kilogram, and the two figures that cover almost all approved use are 150 mcg/kg and 200 mcg/kg. What changes between conditions is not usually the size of the dose but how many doses are given and how far apart.
150 mcg/kg, single dose is the regimen for onchocerciasis (river blindness), repeated every 6 to 12 months.
200 mcg/kg is the standard for strongyloidiasis (once daily for two consecutive days) and for scabies (one dose repeated after 7 to 14 days).
Higher doses have been studied. Trials examining up to 800 mcg/kg found no significant increase in adverse effects at those levels in healthy adults, but that is a research finding rather than a recommendation, and dosing above standard should only happen under clinical supervision.
Working from the 200 mcg/kg figure, an adult of 50 kg needs about 10 mg, 60 kg about 12 mg, 70 kg about 14 mg, 80 kg about 16 mg, 90 kg about 18 mg, and 100 kg about 20 mg per dose. At 150 mcg/kg the same weights need roughly 7.5 mg, 9 mg, 10.5 mg, 12 mg, 13.5 mg and 15 mg.
Because tablets come in fixed strengths, real-world dosing rounds to the nearest achievable combination. Ivermectin has a wide therapeutic window, so modest rounding upward is normally well tolerated — but the calculation should still start from actual body weight rather than a guess.
This matters more than most people realise. Pharmacokinetic studies have found that a high-fat meal roughly doubles ivermectin bioavailability compared with taking it fasted. The original labelling advised an empty stomach, but current practice in many settings is to take it with food precisely because absorption is so much better.
The practical implication is that the same tablet can deliver substantially different plasma concentrations depending on whether it was taken with a meal. Consistency matters when a course spans multiple doses.
Ivermectin kills larvae and adult parasites but does not reliably kill eggs. In scabies, eggs already laid in the skin hatch over the following week; in strongyloidiasis, the autoinfection cycle continues. The repeat dose at 7 to 14 days catches the newly hatched generation before it can mature and reproduce.
Skipping the second dose is one of the most common reasons a course appears to fail.
Oral ivermectin has generally been limited to people above 15 kg, though studies in smaller children have been reassuring. In pregnancy, data are limited and treatment is usually deferred where it can safely wait. It passes into breast milk in small amounts.
People taking warfarin need INR monitoring. Anyone on drugs that inhibit P-glycoprotein, or with liver or kidney impairment, should be dosed under clinical supervision. See the full safety and interactions guide.
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View products and pricingStandard dosing is 150 to 200 mcg per kilogram depending on the condition. At 200 mcg/kg that is roughly 12 mg for a 60 kg adult, 14 mg at 70 kg, 16 mg at 80 kg and 20 mg at 100 kg. Always start the calculation from actual body weight.
Pharmacokinetic studies show a high-fat meal roughly doubles absorption compared with fasting. Original labelling advised an empty stomach, but taking it with food is now common practice precisely because bioavailability is so much higher.
Ivermectin does not reliably kill parasite eggs. The repeat dose at 7 to 14 days kills the generation that hatches after the first dose, before it can mature and reproduce. Skipping it is a common cause of apparent treatment failure.
Not necessarily, and it raises risk. Trials have examined doses up to 800 mcg/kg without a significant rise in adverse effects in healthy adults, but that is a research finding, not a recommendation. Neurological risk rises with dose, particularly alongside P-glycoprotein inhibitors.