Final answer:
Ganciclovir is used as prophylaxis and treatment for CMV infection in HIV-positive patients, particularly effective against CMV retinitis by inhibiting the viral DNA replication.
Step-by-step explanation:
The medication commonly used both as prophylaxis and treatment of Cytomegalovirus (CMV) infection in HIV-positive patients is Ganciclovir. Ganciclovir is an antiviral drug that is structurally similar to a DNA nucleoside. When integrated into the viral DNA during replication, it functions to halt the copying process, thereby inhibiting the virus's ability to multiply. This mechanism is crucial in managing CMV retinitis, a potentially severe infection of the retina that can occur in immunocompromised individuals, including those with HIV/AIDS. Ganciclovir is a critical component of the therapeutic regimen for preventing and treating CMV infections