CMV retinitis

[Cristagali]

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Whats FIRST DOC? Ganciclovir? or Foscarnet? Thanks 😎

 

[Idiopathic]

Ganciclovir first, foscarnet if resistant...do you remember what the MOA is of each?

 

[Cristagali]

Without peeking at my FA, Ganciclovir needs viral thymidine kinase to be activated while Foscarnet does not. So if I get a question about CMV retinitis and both drugs are listed...I should choose ganciclovir?

 

[Idiopathic]

Yes...foscarnet is an extremely toxic pyrophosphate analog, i believe.

More than likely, the question would give you CMV retinitis, and then ask the MOA of the drug of choice, which is ganciclovir.

 

[Cristagali]

Ahha...those tricky bast@!rds. So thats how they ask the question. Won't even mention the drug!! 😀

 

[Long Dong]

Ganciclovir needs viral thymidine kinase to be activated while Foscarnet does not. So if I get a question about CMV retinitis and both drugs are listed...I should choose ganciclovir?

I thought that was acyclovir (not sure of spelling) that messed with thymidine kinase?

 

[Idiopathic]

All the cyclovirs require viral thymidine kinase to be activated, which is why they are selectively toxic to virally infected cells.

 

[DOapplicant]

well, i believe that both acyc and gang need to be act by a TK.
the diff is that acyc is act by vTK; many herspes viridae posses this enz but cmv does NOT. gang is act by human TK. therefore it is eff against cmv; subsequently also eff against other herpes viridae but not prefer in those cases over acy b/c its tox is more threatening.

hope that helps

ps if that doesn't sound right you might want to check it up (i haven't yet)

 

[Idiopathic]

I think we are nitpicking here. Ganciclovir is converted to an active metabolite by a cellular thymidiine kinase that is induced by CMV infection, not by a viral thymidine kinase. But a good point nonetheless.

 

[Cristagali]

But I've never "seen Acyclovir and CMV in the same sentence". I wouldn't start with acyclovir...I just wanted to clarify the "CMV retinitis", versus just a diagnosed case of "CMV hepatitis", etc. 😀 Thanks for the feedback

 

[irlandesa]

oh, I'm on my ID rotation and I got pimped on this the other day b/c of one of my patients..Here is my understanding; if the clinical picture is more typical of CMV retinitis than acute retinal necrosis caused by VZV (i.e. there are no zoster lesions), then use gancyclovir. If there is serious reason to suspect potential co-infection from CMV + VZV (unclear clinical picture and probably severely immunosuppressed patient), then you can use foscarnet, but outside of the BMT floor, it is not commonly used. And if the clinical picture suggests acute retinal necrosis (i.e. rapidly progressive vision loss oft. accompanied by swelling + erythematous, necrotic looking sclera) secondary to VZV (and sometimes HSV), go with acyclovir ONLY.

 

[Idiopathic]

oh, I'm on my ID rotation and I got pimped on this the other day b/c of one of my patients..Here is my understanding; if the clinical picture is more typical of CMV retinitis than acute retinal necrosis caused by VZV (i.e. there are no zoster lesions), then use gancyclovir. If there is serious reason to suspect potential co-infection from CMV + VZV (unclear clinical picture and probably severely immunosuppressed patient), then you can use foscarnet, but outside of the BMT floor, it is not commonly used. And if the clinical picture suggests acute retinal necrosis (i.e. rapidly progressive vision loss oft. accompanied by swelling + erythematous, necrotic looking sclera) secondary to VZV (and sometimes HSV), go with acyclovir ONLY.

I think for step 1:

gancyclovir for CMV only
acyclovir for any other 'herpes virus' problem
foscarnet for gancyclovir-resistant AIDS-related CMV retinitis