Drug interactions

Hello,
My question concerns co-existing HSV-2 history and chemotherapy for breast Ca. Unfortunately I have been diagnosed with breast Ca, surgery mastectomy and beginning chemotherapy in Jan. Additionally, I have a history of HSV-2 and have had positive results on preventative therapy with valtrex, 500mg daily. Outbreak free x 6yrs. Otherwise healthy.
My question, is it safe to continue preventative treatment during the course of chemotherapy? Should I expect frequent recurrences while on chemotherapy? How prevalent are the recurrences? Will taking the valtrex further depress my immune system?
Are there any contraindications? I would appreciate any feed back on your part.

[Fernando Roque, MD]

Hi Pat,

I checked valacyclovir (valtrex) against four drugs commonly used in treating breast cancer for drug interactions.  The drugs are Cyclophosphamide, Doxorubicin, Paclitaxel and Docetaxel.  There does not seem to be any significant adverse effects/ interactions when any of these are used with valtrex, so you can continue using it even if you're given any of the four drugs mentioned above.

While on chemotherapy, your immune system will be down, so there is a danger that any latent HSV infection may flare up.  This is why it becomes very important for you to continue taking valtrex during chemotherapy, so that such HSV recurrences can be prevented.

As far as I know, valtrex will not depress your immune system any further than it will be lowered by the chemotherapy.  Valtrex should be used with caution if you have any problems with the functioning of your kidneys, but it is not totally contraindicated. The dose of valtrex just has to be reduced for those with renal impairment.