The trials so far have shown ivermectin reduces the number of cell-associated viral RNA by 99.8 % in 24 hours. This was an in vitro study which means they were testing cells in a laboratory and not in a living organism.
We will be waiting for clinical trials in patients to see how well ivermectin works in treating COVID-19. They will be testing whether ivermectin decreases the symptoms, time for recovery and death rate from COVID-19.
As Ivermectin is already a FDA approved medicine we already know that it has been established as safe for human use.