When I feel one coming on, I take Acyclovir orally, and also apply a prescription ointment to the area (the name escapes me, but your doc would know.) This helps treamendously. Also, I take ibuprofen for the discomfort, and sometimes add a topical treatment like orajel if the pain is too bad.

I was prescribed Acyclovir by my doctor...it's an oral medication and has worked just dandy for me.