I haven't used my Acyclovir 400 MG in a very long time since my first break out about 4 years ago My Acyclovir 400 mg expired 8 months ago. I started getting a cold sore last Wednesday. By Sunday the cold sore was getting worse so I started taking my acyclovir pills 3times a day. Since they are expired Can I still take them and can I up the dosage to six times a day to get rid of a cold sore, and for how long should I take them? It is Tuesday and I can't tell if the cold sore is getting better or worse.