I currently take Valtrex for cold sore outbreaks, 2 pills at first sign, then 2 pills 12 hours later. Right now I'm traveling overseas and feel an outbreak coming on. Unfortunately, I only have 2 Valtrex pills left, and I'm having a hard time reaching my doctor back home to renew this prescription (there are no refills left on this one.) I did take the first dose of Valtrex, thinking I had 12 hours to reach my dr and have the rx called in, however I haven't been able to reach him. I just found out that a family member has Acyclovir. My question is, can I take Acyclovir for the second dose, 12 hours after taking the first dose of Valtrex?