Valacyclovir 500mg is an antiviral medication used to treat infections caused by herpes viruses, including herpes labialis (cold sores), genital herpes, herpes zoster (shingles), and chickenpox. It works by preventing the herpes virus from multiplying in the body, thereby helping to control symptoms and speed up healing. Valacyclovir is converted in the body to acyclovir, the active drug that inhibits viral DNA replication. It does not cure herpes infections but reduces their severity and frequency. Valacyclovir is usually taken orally, and patients are advised to stay hydrated during treatment.