[Leica] color blind...

[allen.graves at charter.net (Allen Graves)]

Chloroquine (used for treating malaria) and its cousin, Plaquenil 
(hydroxychloroquine)-used for treating rheumatologic disorders like 
lupus- can also cause color blindness.

When I use ethambutol  the normal screening for retinal toxicity is 
to check color vision IF the drug is going to be used for more than 2 
or 3 months. It takes several months for toxicity to develop and it 
is usually reversible if detected early. Screening is usually every 
month or two after the first 3 months. If  is continued too long 
after toxicity develops it can cause macular degeneration. We usually 
use ethambutol for 2 months and then discontinue it.

The risk of toxicity from ethambutol is quite small compared to the 
risk of dying from untreated drug-resistant tuberculosis.

I've never used chloroquine for long enough to have to bother with 
vision screening. Patients on Plaquenil are usually screened every 6 
months or so.

As far as I know, the mechanism of ethamutol toxicity is direct 
toxicity to the retinal receptor cells. The cones, which detect 
color, seem to be more sensitive and develop problems earlier (if 
problems are going to develop-I've only seen this once), allowing 
color vision to be used as a screening tool.

I am unable to find any problems with color  blindness caused by the 
sort of antibiotics used for sepsis.

Allen

>hi Greg, a fascinating question, yours... I will tell you what I 
>have found so far, and I'll share it with the LUG list...
>
>ethambutol, a drug which is part of multidrug TB therapy, can 
>sometimes affect vision and especially color vision.
>
>this seems to be generally what is referred to, when we google...
>
>(I am not sure what the mechanism is...)
>
>  I am also checking to see if any of the customary antibiotics that 
>are used to treat bacterial sepsis, may also cause risk...though of 
>this I don't know, but I'm further searching the medical 
>literature...and if I find something I'll let you know.
>
>It's a provocative question... one that I have never seen 
>investigated in questions of antibiotic toxicity, with the exception 
>of the drug ethambutol...
>the LUG sure can be an amazing source of information,
>
>Steve
>
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