mircro question

[firstaid2012]

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what do you use to treat a latent HSV and VZV infection. if acyclovir doesnt work on latent forms

 

[ashik33]

Nothing

 

[Phloston]

what do you use to treat a latent HSV and VZV infection. if acyclovir doesnt work on latent forms

I've encountered in a practice question that during latency, daily valacyclovir decreases the # of subsequent episodes (i.e. decreases recurrence). "One-time acyclovir infusion" was also an answer, but that was incorrect. Relapsing episodes are prevented with daily valacyclovir, not one-time acyclovir.

The Val- prefix = increased oral bioavailability. It means the drug is generally good to use at home.

However, during outbreaks, one-time acyclovir is best, as it can reduce the duration by ~50%.

Now here's the thing. You asked about what if acyclovir doesn't work. If acyclovir doesn't work, then valacyclovir doesn't work either.

Acyclovir / valacyclovir should be effective against HHV1-4 insofar as viral thymidine kinase is present. Resistant HHV strains tend to have not modified, but instead absent viral thymidine kinase (I've also seen this in a practice question).

In the case of HHV1-4, you give cidofovir, because it doesn't require that initial viral-induced phosphorylation because it is already a cytosine nucleotide, which means it's already monophosphorylated.

The viral kinases always generate the monophosphates (nucleotides) from the nucleosides. Then the host cell kinases generate the triphosphates from the monophosphates (think of this as a flowchart). Cidofovir and foscarnet both bypass the first step, so they're not dependent on the presence of the viral thymidine kinase.

Cidofovir is typically used for acyclovir-refractory HHV1-4 and foscarnet for HHV5 (CMV), although cidofovir can also be used for CMV retinitis (same as foscarnet).

All of these drugs are nephrotoxic. That's something to remember. I've also seen that in practice questions. And you always administer cidofovir with probenecid. This is all actually in FA IIRC.

 

[firstaid2012]

thank you so much for the explanation it was great! i saw it in firstaid it said acyclovir didnt work on latent forms.

i also have a biostats question if you could help me out.

it says if the CI for a mean diff between 2 variables includes 0, then there is no signifcant diff and h0 is not rejected. if the 95 % for odds ratio or relative risk includes 1, h0 is not rejected. if the CI between 2 groips overlaps then these groups are not significantly different. could you please explain. thank you