IC50 of minocycline

[Guest guest]

I dont think this is a free text. But if you can get it, check out

fig 2d, an E coli based cell-free translation inhibition assay for

mino and tetracycline:

http://aac.asm.org/cgi/reprint/50/6/2156.pdf

The IC50 is only about 2 uM for mino. Thats about 1.6 ug /mL. Figure

in a 3x cellular/extracellular ratio, and you only need a serum level

of ~0.5 ug /mL to achieve 50% protein synthesis inhibition in an

intracellular bug (one that neither concentrates nor excludes mino).

In message 8080 I loosely calculated a 1.6 ug /mL serum Cmax for 40

mg daily use of doxy, which is supposedly sub-antimicrobial. The Cmax

for 20 mg bid (which is what they actually used) will be lower, but

not lower than 0.8 ug /mL. Still probably high enough that youll

reach the IC50 inside some host cells.

Assuming doxy has an IC50 similar to minos (which I am not sure of),

that most bacteria do not concentrate or exclude doxy (which I am not

sure of), and that 50% protein synthesis inhibition can slowly impact

a putative bacterial population (and hence inflammation) in some

disease X, then this assumption that 40 mg of doxy a day cant be

antimicrobial should be rejected.