Valacyclovir (Valtrex) is an antiviral medication used for treating infections caused by herpes simplex virus and varicella zoster virus, such as cold sores, genital herpes, and shingles, and chickenpox. Overview: Valacyclovir is an antiviral medicine used to treat conditions such as cold sores, genital herpes, shingles, and chickenpox. It works by stopping the growth of herpes viruses. Common. Valacyclovir is used to treat infections caused by certain types of viruses. Learn about side effects, drug interactions, dosages, warnings, and more. Valaciclovir, also spelled valacyclovir, is an antiviral medication used to treat outbreaks of herpes simplex or herpes zoster (shingles). [2] It is also used to prevent cytomegalovirus following a kidney transplant in high risk cases. [2] Valacyclovir is used to treat cold sores (herpes labialis), shingles (herpes zoster), and genital herpes. It is also used to control genital herpes outbreak in patients with human immunodeficiency virus-1 (HIV-1). Detailed Valacyclovir dosage information for adults and children. Includes dosages for Herpes Simplex Labialis, Herpes Simplex - Suppression, Herpes Zoster and more; plus renal, liver and dialysis adjustments. Valacyclovir is an antiviral drug. It slows the growth and spread of the herpes virus to help the body fight the infection. Valacyclovir is used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles (herpes zoster) in adults.