Antiviral drugs

Encyclopedia of Medicine, Apr 06, 2001 by Nancy Ross-Flanigan

Older people may be especially sensitive to the effects of some antiviral drugs. This may increase the chance of side effects.

Drinking alcoholic beverages while taking certain antiviral drugs may increase the chance of side effects. Anyone who takes these drugs should check with a physician before drinking alcohol or taking medicines that contain alcohol.

When taking an antiviral drug to prevent flu, start taking the medicine before, or as soon as possible after, being exposed to people who have the flu.

When taking an antiviral medicine for chickenpox, shingles, or herpes infection, start taking the medicine as soon as possible after the symptoms appear. The medicine may not be as effective if too much time passes.

Patients who are taking an antiviral drug for herpes should keep in mind that the medicine will not prevent them from spreading the infection to other people. They must still take these precautions to avoid passing the virus through sexual contact:

Avoid any sexual activity if either partner has sores or other symptoms of herpes Use either a male or female condom at other times.

Ganciclovir can cause serious problems with the blood. This can increase the risk of infection or excessive bleeding. Anyone who plans to take this drug should thoroughly discuss the benefits and risks with his or her physician. While taking ganciclovir, take these precautions to help reduce the risk of infection and bleeding:

• Visit the physician and have blood tests as often as the physician recommends
• Call the physician immediately if sore throat, fever, chills, or other signs of an infection occur
• Call the physician immediately if any of the following occur: unusual bleeding or bruising; black, tarry stools; blood in the urine or stools; red, "pinpoint" spots on the skin
• Take care to avoid injuries when shaving, cutting fingernails or toenails, brushing or flossing the teeth, or using any sharp instruments.

Valacyclovir (Valtrex) should not be used by anyone with a weakened immune system, such as people with HIV infection or patients who have had bone marrow or kidney transplants. The medicine can cause serious and life-threatening side effects in these people.

People with certain other medical conditions or who are taking certain other medicines can have problems if they take antiviral drugs. Before taking these drugs, be sure to let the physician know about any of these conditions:

Anyone who has had unusual reactions to antiviral drugs in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

Women who are pregnant or who may become pregnant should check with their physicians before using antiviral drugs. Some may be safe to use, but others may cause birth defects. In particular, ganciclovir should not be used during pregnancy, and both men and women who are sexually active should use effective contraceptives when being treated with ganciclovir. Men should use condoms during treatment with this drug and should continue to use condoms for at least 90 days after treatment ends. Ganciclovir may also cause fertility problems.