A new paper is circulating, leading to a new & improbable claim that "ivermectin treats staph aureus."
There is absolutely no evidence that this is true.
A short thread about pharmacology (MICs, IC50s, and Cmax) explaining why this claim is so unlikely.
1/
There is absolutely no evidence that this is true.
A short thread about pharmacology (MICs, IC50s, and Cmax) explaining why this claim is so unlikely.
1/
This paper by Ashraf et al is an in vitro study of repurposed meds on MRSA & MSSA.
Right off the bat, there are weird things going on. They grew 21 strains and report results for...2
And when they treated those strains with ivermectin, they used some insanely high doses...
2/
Right off the bat, there are weird things going on. They grew 21 strains and report results for...2
And when they treated those strains with ivermectin, they used some insanely high doses...
2/
How high?
They found the minimum inhibitor conc (MIC) to kill MSSA was 12.5 ug/mL
How high is that? Let's do some math:
Ivermectin has two forms B1a & B1b. The average MW is 868 g/mol.Converting 12.5 ug/mL mass concentration to molar concentration we get 14 uM! Yikes!
3/
They found the minimum inhibitor conc (MIC) to kill MSSA was 12.5 ug/mL
How high is that? Let's do some math:
Ivermectin has two forms B1a & B1b. The average MW is 868 g/mol.Converting 12.5 ug/mL mass concentration to molar concentration we get 14 uM! Yikes!
3/
Is an MIC of 14 uM a lot?
Well, when people take ivermectin as prescribed (0.2mg/mL daily) the plasma level is *much much* lower: The Cmax for ivermectin is ~50 nM (or 0.05 uM).
The in vivo dose (Cmax) is way less than the dose required in vitro (MIC): 280x lower in fact!
4/
Well, when people take ivermectin as prescribed (0.2mg/mL daily) the plasma level is *much much* lower: The Cmax for ivermectin is ~50 nM (or 0.05 uM).
The in vivo dose (Cmax) is way less than the dose required in vitro (MIC): 280x lower in fact!
4/
Incidentally this is the same reason that many of us were skeptical that ivermectin could inhibit SARS-CoV-2 in vitro.
In that case the dose required in vitro was 5 uM. Which was "only" 100x less than required.
Here's a 🧵 I did about that from May.
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In that case the dose required in vitro was 5 uM. Which was "only" 100x less than required.
Here's a 🧵 I did about that from May.
https://twitter.com/nickmmark/status/1396807975101091841?s=20
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Bottom line:
- a new dubious in vitro study finds that ivermectin kill MRSA/MSSA at a dose of 14 uM (MIC), which is 280x higher than can actually be achieved in people
- So IVM kills MRSA but at a dose that would kill people too
- PSA: don't take IVM to treat MRSA or COVID
6/6
- a new dubious in vitro study finds that ivermectin kill MRSA/MSSA at a dose of 14 uM (MIC), which is 280x higher than can actually be achieved in people
- So IVM kills MRSA but at a dose that would kill people too
- PSA: don't take IVM to treat MRSA or COVID
6/6
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