Ivermectin is thought to inhibit the virus by preventing viral proteins moving in and out of the host cell's nucleus, which is essential for replication of the coronavirus.
The problem is this process requires very high concentrations of ivermectin—well above the recommended dose for humans. This means ivermectin's virus-killing powers would be unlikely to be harnessed inside the human body.
A detailed analysis of the relationship between dose and concentration of ivermectin suggests none of the currently used ivermectin dosing regimens would deliver high enough concentrations of ivermectin inside the body to activate its virus-killing effects.
Another review backs this up, suggesting all of the ivermectin doses being investigated in current clinical trials would fall well short of achieving drug concentrations high enough to wipe out SARS-CoV-2.
Even a 120 mg dose of ivermectin, which would be regarded as excessive (compared with the recommended dose of 3-15mg for treating parasitic infections) resulted in blood concentrations several orders of magnitude times lower than those needed to inhibit the virus.
How much ivermectin is too much?
While ivermectin generally doesn't cause problematic side effects at the currently used doses, there is limited information about whether much larger doses would also be safe.
Repurposing ivermectin as a "cure" for COVID-19 would require massive doses, which would substantially increase the risk of side effects such as nausea, rash, dizziness, immune suppression, abdominal pain, fever, raised heart rate and unstable blood pressure.
