Ivermectin is an antiparasitic medicine that attacks the nervous system of worms and other parasites. As viruses are not alive and have no nervous system, or really any organized system, for that matter, one wouldn't expect Ivermectin to have any effect against Covid or other viruses. It's the same reason that antibiotics are useless in preventing or treating viral diseases. Now it may very well have other minor effects that could potentially be used to treat Covid, but I haven't seen any studies on it, just speculation and anecdotes. That said, the whole "horse dewormer" narrative is quite tiring, a human version of Ivermectin (with different dosages) has been developed for human use, and the media is whipping itself into a frenzy over what is, at best, an ineffective treatment that may have some temporary effects like diarrhea but nothing long term.