Probably the most common form of herpes is the common cold sore or fever blister. Valaciclovir is most effective when taken within 24 hours of the start of symptoms. Valtrex can greatly decrease the length of time you experience an outbreak and may possibly reduce the number of outbreaks you have. You will need to practice safe sex for the rest of their life. It is prescribed. You will need to practice safe sex for the rest of your life.