Antiviral Medications

Antiviral drugs are medicines that cure or control virus infections.

Exclusive of the antiretroviral agents used in HIV (AIDS) therapy, there are few antiviral drugs available, and only cover four types of virus. Acyclovir (Zovirax), famciclovir (Famvir), and valacyclovir (Valtrex) ective against the herpes virus, including herpes zoster and herpes genitalis. They may also be of value in either conditions caused by herpes, such as chicken pox and shingles. These drugs are not curative, but may reduce the pain of a herpes outbreak and shorten the period of viral shedding.

Amantadine (Symmetrel), oseltamivir (Tamiflu), rimantidine (Flumadine), and zanamivir (Relenza) are useful in treatment of the influenza virus. Amantadine, rimantadine, and oseltamivir may be administered throughout the flu season as preventatives for patients who cannot take influenza virus vaccine.

As a class, the antivirals are not curative, and must be used either prophylactically or early in the development of an infection. Their mechanism of action is typically to inactivate the enzymes needed for viral replication. This will reduce the rate of viral growth, but will not inactive the virus already present. Antiviral therapy must normally be initiated within 48 hours of the onset of an infection to provide any benefit. Drugs used for influenza may be used throughout the influenza season in high risk patients, or within 48 hours of exposure to a known carrier. Antiherpetic agents should be used at the first signs of an outbreak. Anti-cytomegaloviral drugs must routinely be used as part of a program of secondary prophylaxis (maintenance therapy following an initial response) in order to prevent reinfection in immunocompromised patients.