Valganciclovir is an antiviral medication primarily used to treat infections caused by the cytomegalovirus (CMV), particularly in individuals with weakened immune systems, such as those undergoing organ transplants or living with HIV/AIDS. It works by inhibiting the replication of the virus, helping to control the infection and prevent complications. This medication is usually taken orally in the form of tablets. It is important for patients to follow their healthcare provider's instructions regarding dosage and duration of treatment to ensure effectiveness and minimize potential side effects, which can include nausea, diarrhea, and changes in blood cell counts.