USMLE Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter · #1 ·
ok, here is my problem. I am familiar with the function and such however I am not clear as to how Methemoglobin allows "cytocrome to function" according to FA (pg 478 2009 ed)

Presumably after such binding of cyanide with thiosulfate the cyanide is excreted in the urine via thiocyanate. Where then does the cytocrome oxidase come into play?

Cheers
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #2 ·
any ideas will help guys; come on, there must be some theories out there if not the answer itself. :)
 

·
Registered
Joined
·
51 Posts
The way that cyanide kills you is that it inhibits your cytochrome oxidase... thus inhibiting aerobic respiration....

Now to treat this posoning amyl nitrite is used which converts hemoglobin to methemoglobin... now the whole reason this is done is because HCN has a higher affinity for methemoglobin than cytochrome oxidase and thus HCN will dissaociate from the Cytochrome oxidase (now the aerobic respiration can resome) and bind to methemoglobin.

i dont know if it is in the 2009... just a heads up... but there is a newer technique used to treat HCN poisoining that doesnt involve methemoglobin at all... it uses hydroxocobalamin, another molecule which HCN has a higher affinity for than Cytochrome oxidase and thus is excreted as cyanocoboalmin. I think it is menotioned in the 2010 FA...
 
1 - 3 of 3 Posts
Top