A report dated 4/3/20 indicates that another widely available drug may be effective against the coronavirus:
https://www.sciencedirect.com/science/article/pii/S0166354220302011
A very brief report, on a drug I knew nothing about,
Ivermectin. It is already approved by the FDA to treat parasite infestations. It does show anti-viral activity, but the tests were done on cells growing in culture, infected with SARS-CoV-2. It required concentrations of at least 2 to 3 µM (micromolar) to be effective. (See EDIT below)
It would have been interesting to see Ivermectin's anti-viral activity directly compared, using the same lab model, to that of other drugs, such as remdesivir or hydroxychloroquine.
Can those 2-3 µM concentrations be achieved, safely, in an animal model of Covid-19 or in human patients? Because this drug is already used in humans, I suspect that answer may be known, but I didn't find it with a quick & dirty search.
It appears to be a systemic oral drug. As an anti-parasite drug, it's given as a single dose, with a possible repeat dose every 3 to 12 months. What dose & schedule would be needed for patients with Covid-19?
Does the drug get to the affected respiratory tract tissues at the needed concentration?
Is it effective in severely ill hospitalized patients who already need ventilator? Covid-19 patients and patients with a parasitic disease are a very different patient population. A clinical trial might be needed to test this drug in patients with Covid-19.
EDIT: It looks like concentrations of 2 to 3 µM cannot be achieved in humans. With an Ivermectin molecular wt of 875.1 g/mol, 2 µM becomes about 1750 ng/mL.
The highest plasma concentration after a single oral dose in a phase 1 clinical trial was 81 ng/mL, more than 20-fold lower. Ivermectin is highly soluble in lipids, and as a result, it may be available at higher concentrations in cell membranes that what was measured in patient plasma (cell-free blood). This has to be worked out before this drug can be considered. I don't know if other ways are available to give this drug to get >20-fold higher concentrations in the blood. But with this data, it doesn't look good for Ivermectin to treat Covid-19.