Idebenone can be toxic or beneficial depending on its oxidation-reduction state.

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Idebenone is a CoQ10 clone that is smaller and will pass the BBB. I have some and have taken it a few times but I don't anymore. Every once and awhile I reconsider it. Not going to be restarting it this week. Just too many question marks.

The effects of idebenone on mitochondrial bioenergetics 2012 ncbi.nlm.nih.gov/pmc/articl...

The mitochondrial effects of idebenone in living cells are poorly characterized. ► Idebenone can be toxic or beneficial depending on its oxidation-reduction state. ► Idebenone is toxic through opening of the permeability transition pore. ► Idebenol stimulates respiration and ATP synthesis in cells lacking complex I. ► Short-chain quinones can be developed for the treatment of complex I defects.

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Ferroptosis: molecular mechanisms and health implications 2021 nature.com/articles/s41422-...

Idebenone, a hydrophilic analog of CoQ10 with antioxidant properties, inhibits FIN56- or RSL3-induced ferroptosis, but promotes staurosporine-induced apoptosis through an as yet elusive mechanism.