I am experiencing cold sore breakouts after my laser tattoo removal sessions. How can I prevent this?

So far I've had two laser sessions. Each time, I've gotten a cold sore about 5 days after the treatment. I've heard I can use my Valtrex prescription as a preventative. Normally, I would take Valtrex (2 pills, 2 times per day) at the first sign of a cold sore, until all the pills are gone. In this case, how exactly would you recommend I take the pills once it's time for my next laser tattoo removal session. This treatment seems to trigger my immune system and the virus. Thank you.