What medication is primarily used to treat Cytomegalovirus infections?

Ganciclovir is primarily used to treat Cytomegalovirus (CMV) infections, particularly in immunocompromised patients, such as those with HIV/AIDS or transplant recipients. CMV is a member of the herpesvirus family, and ganciclovir is specifically designed to target viral DNA synthesis. It acts as a synthetic analog of guanosine, getting phosphorylated by the viral enzyme kinase, which allows it to inhibit the viral DNA polymerase effectively, blocking the replication of CMV.

While other antiviral medications have activity against different viruses in the herpesvirus family (like acyclovir, which is primarily used for herpes simplex virus), ganciclovir has a more selective efficacy against CMV, making it the first-line treatment choice for managing these specific infections. Foscarnet is also used for resistant strains but is considered a second-line option due to its toxicity profile. Valacyclovir is another antiviral but it is primarily used for infections caused by herpes simplex virus and varicella zoster virus, not CMV. Thus, ganciclovir is the most appropriate medication for treating CMV infections.