Valacyclovir: learn about side effects, dosage, special precautions, and more on MedlinePlus 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. A practical guide to Valacyclovir and Valtrex - what they are, how they are used, benefits, risks, side effects, comparisons, and answers to common questions. Valacyclovir is used to treat infections caused by certain types of viruses. Learn about side effects, drug interactions, dosages, warnings, and more. Your trusted medical portal for detailed information on antiviral medications like Famvir (Famciclovir), Valtrex (Valacyclovir), and more. Find instructions, comparisons, and research links. VALACYCLOVIR (val ay SYE kloe veer) helps manage infections, such as cold sores, genital herpes, shingles, and chickenpox, caused by viruses. It will not treat colds, the flu, or infections caused by bacteria. 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). Valacyclovir is an oral antiviral and a prodrug of acyclovir. It is used to treat herpes zoster (shingles), genital herpes (initial and recurrent episodes, and in selected patients as suppressive therapy), and cold sores (herpes labialis). Medscape - Herpes simplex, zoster-specific dosing for Valtrex (valacyclovir), frequency-based adverse effects, comprehensive interactions, contraindications, pregnancy & lactation schedules, and. Find patient medical information for Valacyclovir (Valtrex) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings.