Valacyclovir is the generic version of Valtrex®, an antiviral medication pill that lessens the frequency of cold sores and symptoms of oral and/or genital herpes, reducing the chance that you’ll pass the virus to a partner. You can take Valacyclovir when you feel an outbreak coming on to lessen symptoms, or take a dose every day for prevention. Valacyclovir is safe and effective, and side effects are rare.