Ethambutol is a bacteriostatic drug used to treat colour-blindness. It is reported that red-green colour-blindness is produced in patients taking Ethambutol.
Can anyone help me to understand this mechanism?
Ethambutol has a toxic effect on the retinal ganglion cells. That damage often can manifest as a blue-yellow loss early on but as the damage progresses one can also observe red-green defects. e.g. see Polak BC, Leys M, van Lith GH. Blue-yellow colour vision changes as early symptoms of ethambutol oculotoxicity. Ophthalmologica. 1985;191(4):223-6.
The mechanism is excitotoxic damage. See Heng JE, Vorwerk CK, Lessell E, Zurakowski D, Levin LA, Dreyer EB. Ethambutol is toxic to retinal ganglion cells via an excitotoxic pathway. Invest Ophthalmol Vis Sci. 1999; 40(1):190-6.
Good response from Carl. Just to add a couple of more recent references: Semin Ophthalmol. 2007 Jul-Sep;22(3):141-6. and Hong Kong Med J. 2006 Feb;12(1):56-60. It has to be stressed also that typical color vision screening tests (e.g. Ishihara, etc) do not have sensitivity in detecting mild blue-yellow deficits, and, therefore, are not so useful in detecting early toxicity; therefore, arrangement tests like D-15, desat.D-15, R-28 or FM-100 would be better.
Thank you Carl and rad.
Hope these references will be helpful for me.
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