Antiviral Therapy Health Article

Definition

Antiviral therapy is often used by cancer patients to treat viral infections. Commonly used antiviral medications include acyclovir, famciclovir, ganciclovir, valacyclovir, and foscarnet.

Description

Viral infections occur in almost all people at some time in their lives. The common cold is the most easily recognizable example of a virus that can be unpleasant but generally does not cause serious problems. For people with cancer, however, viruses can often cause life-threatening illnesses.

Viral infections in cancer patients can be much more serious and debilitating than in patients without cancer. Cancer patients will often have weakened immune systems from chemotherapy or from the cancer itself. Cancer patients who have bone marrow transplants are at especially high risk for life-threatening viral infections. Immediately after the transplant, the patient will have very few, if any, white blood cells, which are the body's main infection fighters. Viral infections such as herpes simplex virus (HSV), herpes zoster virus (HZV), and cytomegalovirus are often seen in cancer patients, and all can cause serious, life-threatening infections.

Until the development of the antiviral drug acyclovir 1974, no relatively safe and effective anti-viral medications for cancer patients were available. By the mid-1980s, acyclovir was being routinely used for cancer patients with herpes infections. Besides treating the infection itself, acyclovir can be taken on a daily basis to prevent infection from occurring. This can be especially important in people with very depressed immune systems, such as cancer patients who have undergone a bone marrow transplant.

Since the introduction of acyclovir, other anti-viral medications have been developed that have been very useful in the treatment of viral illnesses. For reasons that are still unknown, certain herpes infections in certain cancer patients do not respond to acyclovir. Fortunately, two other newer medications similar to acyclovir, called famciclovir and valaciclovir, are helpful in treating herpes infections, especially ones that are resistant to acyclovir.

While antiviral drugs such as acyclovir have made a large difference in treating herpes infections in cancer patients, there are other viral infections that do not respond to acyclovir. Cytomegalovirus is a common viral infection among cancer patients, and especially common among cancer patients who have had bone marrow transplants. Some antiviral medications like acyclovir are not effective against cytomegalovirus. Fortunately, two other antiviral medications known as ganciclovir and foscarnet are both effective against cytomegalovirus.