Valtrex can harm your kidneys. This risk may increase when you also use certain other medicines, including: antivirals, chemotherapy, certain antibiotics, medicine for bowel disorders, medicine for high blood pressure, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including Advil, Motrin, and Aleve). Ask your pharmacist if you are concerned you are taking other medications that may harm your kidneys.
Other drugs may interact with valacyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.
 Valtrex drug interactions (more detail)
