Acyclovir
"My experience is that I have had cold sores ONLY on my lips from age 6 to 35. I agreed to a 1st date...bam! I felt it. That is the key; take meds once 1st felt.
I have no medical knowledge except I know what my body tolerates and what has been successful which may not be your best bet but be safe careful and consult you Dr b4 any treatment plan. 
1. break up your pills in half for immediate absorbtion take 800mg every 2 hours to slam your system to alert it there's an issue and send in a 2nd round of 800 within 1st 4 hours
2. continue 800 for 2 days every 4 hours
3. apply Abreva or similar product on the sore at first sensation, while taking the meds so you are attacking the infection from inside (meds) and externally (creme on sore)
4 days"