Thread by @alexandrosM

I've tried to stay away from opining on the actual biology of ivermectin as I'm not of that field, but in a recent conversation someone put me in a spot where I was forced to dig deeper on the specifics. And if I have to suffer, might as well write here about what I learned.🧵

This person, who I consider a good person, was referring to @ydeigin's argument on blood plasma half-life being 18 hours, and therefore that a weekly regimen couldn't possibly be efficacious. Yuri has made that argument clearly here:

https://twitter.com/ydeigin/status/1394476273641140232?s=20

The point being that the antiparasitic effects are due to it wiping out all the parasites during the initial spike, not due to it having lasting protective effects from reinfection. First, the bad news: it's true that in an annual or biannual regimen, IVM is only effective if you

also protect against re-infection after the effects of your original dose wear off. However, what I've found is that the available research indicates that the effects don't wear off in the first 18 hours as implied in the argument.

To make this argument most effective, let's stick with anti-parasitic properties instead of antiviral ones. This 1986 paper "The residual effect of treatment with ivermectin
after experimental reinfection with nematodes in
calves" makes the point clearly: tandfonline.com/doi/pdf/10.108…

6 groups of calves were all infected with three different parasites each (ouch!). The first group was left untreated. All the other 5 groups were treated with ivermectin 21 days after infection. Calves of groups 1 and 2 were slaughtered 7 days after the infection (28 days total)

Calves of groups 3, 4, 5, 6 were reinfected with the same three parasites at different times:

group 3 was reinfected 3 days after treatment.
group 4 was reinfected 1 wk after treatment.
group 5 was reinfected 3 wks after treatment.
group 6 was reinfected 6 wks after treatment.

21 days after reinfection, each of the remaining groups was slaughtered to measure progress of reinfection. Groups 3 & 4, reinfected 3 days and 1 week after treatment with ivermectin for the original infection, were able to return to pre-reinfection levels of parasites or better.

Groups 5 & 6, reinfected 3 weeks and 6 weeks after the treatment of the original infection, did not show a protective effect of ivermectin, as the parasite infections had taken hold and grown to pre-treatment levels.

In other words, in this fairly simple study, ivermectin taken to treat an infection showed protective effects against reinfection that happened 3 and 7 days after treatment, but not against reinfection that happened 3 and 6 weeks after treatment.

Whatever the reason, a weekly regimen of ivermectin doesn't seem impossible to have an effect as presented in the Quillette article and in the above tweet by @ydeigin. A half-life of 18 hours does not prove that whatever residual is left e.g. 180 hours later is ineffective.

And of course as mentioned there could be all sorts of reasons why the effects persist other than plasma concentration:

https://twitter.com/joshuaabooker/status/1417651309650587648?s=19

So, for the more biologically inclined, am I missing anything? Did I read the study correctly? Is there any reason a priori why the results may not translate to humans?

Added to the ivm 🧵🧵

https://twitter.com/alexandrosM/status/1413977110180364294?s=19

@clairlemon treat this as another request for correction on Yuri's and @claireberlinski's article on @BretWeinstein (and by implication his co-host @HeatherEHeying). The 18 hour half-life effect claim doesn't hold up even if we only consider antiparasitic effects.