There's a ton of off-patent medicines. You can't do large-scale trials for all of them, there literally aren't enough COVID patients to do a large-scale trial f

There's a ton of off-patent medicines. You can't do large-scale trials for all of them, there literally aren't enough COVID patients to do a large-scale trial for every off-patent medicine that exists. You have to have some selection criteria. Ivermectin is an anti-parasite drug. It is not an anti-viral. There is no theory for a mechanism of action for why it would be effective against COVID. There is some laboratory evidence that Ivermectin at very high concentrations can inhibit replication of COVID-19 and other viruses. The problem with this is that extrapolating from those concentrations to a dosing regimen means a dose of Ivermectin far, far higher than the dosage of Ivermectin given in humans. So, without sufficient evidence, there's no compelling reason to do a large trial of Ivermectin.