Ganciclovir is primarily used in the treatment of cytomegalovirus (CMV) infections, particularly in immunocompromised patients such as those with HIV/AIDS or individuals who have undergone organ transplants. It works by inhibiting the replication of the virus, thereby controlling the infection and preventing its spread.

In addition to treating active CMV infections, ganciclovir is also used as a preventive measure (prophylaxis) in patients at high risk of developing CMV disease, especially after transplant surgeries. It is effective in reducing the incidence of CMV-related complications, such as retinitis, pneumonia, and gastrointestinal infections.

Ganciclovir is available in various forms, including intravenous, oral, and ocular implants, allowing for flexible administration based on the patient's condition and needs. The ocular implant is specifically used to treat CMV retinitis, a serious eye infection that can lead to blindness if left untreated.

While effective, ganciclovir requires careful monitoring due to potential side effects, such as bone marrow suppression, which can lead to reduced blood cell counts. Regular blood tests are often necessary to ensure patient safety during treatment.