The use of VALTREX for treatment of cold sores is based on double-blind, placebo-controlled clinical trials in healthy adults and adolescents 12 years of age with history of recurrent cold sores see Clinical Studies. Chickenpox: The recommended dosage of VALTREX for treatment of chickenpox in immunocompetent pediatric patients to 18 years of age is 20 mg kg administered times daily for days. The most common adverse reactions reported in at least indication by 10 of adult patients treated with VALTREX and observed more frequently with VALTREX compared to placebo are headache, nausea, and abdominal pain. Before using this medication, tell your doctor or pharmacist your medical rekkefolge kjope valacyclovir online history, especially of: kidney disease, blood disorders, immune system problems.