I suppose that the anti-parasitic effect could explain why doctors in South America and Africa are so adamant about it "working". But the main idea behind iver

I suppose that the anti-parasitic effect could explain why doctors in South America and Africa are so adamant about it "working". But the main idea behind ivermectin being used for covid is actually that it's a protease inhibitor. It essentially could directly prevent the virus from replicating. They found a bunch of repurposable drugs which have that mechanism earlier on in the pandemic, and ivermectin was found to be extremely promising. Researchers just didn't know under what conditions and dosage it would be effective, since during the tests they blasted all of the drugs at maximum potency. Since then, well... I have no idea. It seems like ivermectin would have to be given in very large doses to actually work, or modified to fix that issue. But instead everyone seems to just be trying to test/use the normal anti-parasitic doses, and I haven't seen anyone trying to modify it to bring out the protease inhibitor effect. I think the cases in which it works are probably mostly in people with parasites, but there could be some other circumstance that makes it work sporadically - who knows.