The reason that ivermectin isn't used for covid-19 is because there is weak data to support even doing a randomized trial on humans, especially when we have known effective treatments.
Most of the Pubmed studies on Ivermectin are garbage, and published in garbage journals. Several have been retracted because of said garbageness. A few trials aren't garbage but under-powered, thus unable to identify any real benefits.
The Oxford and Imperial College London groups did a meta-analysis, which tries to piece together garbage into some sensible data. This showed no benefit to any endpoint (survival, hospitalization, time to clinical recovery) after combining data from 3349 patients in 23 RCTs. They also note the overall poor quality of the data, with most RCTs thrown out for various reasons due to poor design. In fact, they had to re-do the analysis after publication because it turns out one of the studies had fraudulent data and was retracted!! If you look closely, the larger the trial, the less "benefit" was seen.
https://pubmed.ncbi.nlm.nih.gov/34796244/
Maybe when we had no effective treatments for covid-19 trying these in a non-experimental setting would be valid ethically, but at this point it is not. There is absolutely no evidence of benefit in severe COVID-19, which is the one scenario where it could even be considered (due to lack of other effective treatments).
Japan is doing reasonably well because they have a very robust track-and-trace program, a well-enforced quarantine program and high vaccination rates.
Yeah, I don't recommend any drug that isn't proven.
At the same time I also remember a few months back when everything you're saying above about Ivermectin applied to Remdesivir too. Fraudulent studies, absolutely no valid evidence of benefit, meta-analysis shows no better than placebo, WHO strongly recommends against usage in any Covid case . . . but here we are now recommending usage since it turns out that the drug works pretty well.
It'll be interesting to eventually find out if any of these other controversial drugs work or don't when all the data is in.
Difference for remdesivir specifically is it had a plausible mechanism of action supported by over a decade of studies in other virus families. This was confirmed in several animal models before proceeding to human trials. Similarly, molnupiravir, the newly approved (on emergency basis) oral antiviral was also developed in a similar fashion (pre-pandemic), and rapidly evaluated in multiple animal models before a large randomized trial confirmed efficacy (albeit limited - 30% relative reduction and 3% absolute reduction in hospitalization). Ritonavir is an old anti-viral with known efficacy in hepatitis B, and was repurposed in combination with other agents for COVID.
Ivermectin does not have this foundation - studies have been limited to rudimentary pre-clinical evaluations on cell lines and mosquito models for specific viruses transmitted in this way. That is more in line with HCQ, for example.
All of that needs to considered in recommendations on use. I know you understand this, but a lot of people do not. I'm just not sure why people are so caught up on ivermectin when we have multiple effective medications.
So far a brief summary:
Anti-parasitic agents:
HCQ - ineffective, potentially harmful
Ivermectin - ineffective
Anti-viral agents:
remdesivir - effective in hospitalized patients
molnupiravir - moderate efficacy for non-hospitalized patients
ritonavir - more effective for non-hospitalized patients (preferred over molnupiravir)
Other agents:
Dexamethasone - effective in hospitalized patients, not effective for outpatients
monoclonal antibodies - effective for outpatients (depending on strain)
polyclonal antibodies (from plasma of recovered COVID patients) - not effective