I can offer some experience with this issue.
I take acyclovir, which is very closely related to valtrex, on a daily basis.
I have genital herpes, but I don't get sores. Instead I have a tiny spot that itches almost all the time if I'm not taking my medication. I am also shedding virus when this is happening, so I decided to go on suppressive therapy.
Shingles is a form of herpes, by the way.
Valtrex and acyclovir are similar to a protein that the virus looks for. Valtrex has more bio-availability but it costs a lot more. The virus takes up the medication and inserts it into its dna. This disables the virus' ability to replicate. It just can't infect new cells. It doesn't kill the virus.
I have taken acyclovir on many occasions when I rolled. In fact I take higher doses during the days leading up to the MDMA. There are no interactions.
In fact you can ignore the above warnings about nausea. All meds have that as a side-effect. You could give WATER to 100 people and 3 of them will report dry mouth!
No interactions at all. But MDMA does effect the immune system.
If I don't take my acyclovir around my roll, my little friend gets fired up and itches like crazy.
Any amphetamine will do this.
If this really is shingles, DO NOT roll until you are clear. It just isn't worth it. You will knock out your immune system. If this is your first herpes outbreak, the same advice applies. The first outbreak is FAR worse than any following one. During the first few months your body will develop antibodies that help to keep the virus in check. But knocking out your immune system during this period of time is a bad idea...
Hope this helped.