Antiviral medications

A virus is an infectious organism that can only grow and reproduce when attached to a living cell. When a virus enters your body, it feeds on healthy cells and uses them for its own survival and reproduction. A virus can survive and be infectious for a period of time outside of a cell, however.

There are more than 400 known viruses that cause human illness in the world today. Some cause mild symptoms, others lead to serious illness and some viruses are fatal. Some viruses remain dormant or hide within cells for years.

Antiviral medications are used to treat viral infections such as hepatitis, influenza, chickenpox, shingles, herpes and AIDS.


General information
There are a limited number of antiviral medications available. Also, viruses have often nearly run their course by the time you develop symptoms or realize you're sick. Treating a virus this late is often difficult. When possible, many antiviral medications are given before or as soon as you're exposed to the virus. This helps prevent the virus from multiplying inside your body, which can decrease the length and severity of your illness.

Common antiviral medications
Antiviral medications are typically taken orally (in pill form), but they may also be injected, inhaled, given intravenously or applied to the skin as an ointment. Some of the more common antivirals are described below.
Acyclovir, famcyclovir, valacyclovir and penciclovir
Acyclovir (Zovirax, for example) is used to treat certain infections caused by the herpes virus. When taken orally, acyclovir can help prevent or minimize recurrences of genital herpes, speed recovery of an outbreak, reduce pain and decrease the chances of spreading the condition.

The same medication may be given intravenously (into a vein) to treat chickenpox in people who have weak immune systems. It can also help prevent fatalities if a herpes infection travels to the brain and causes a serious infection.

When taken early in the course of shingles (an infection caused by the same virus that causes chickenpox), acyclovir can shorten the duration of the infection and length of contagiousness, as well as decrease the risk of post-herpetic neuralgia (nerve pain after shingles).

Side effects may include:

nausea, vomiting, diarrhea or stomach pain
headache
rash
blood clots where the intravenous catheter (a flexible tube that may be inserted into various parts of the body to inject or remove fluid) is inserted
confusion, tremors, agitation or seizures
changes in kidney function
jaundice
blood in urine
Famcyclovir (Famvir, for example) and Valacyclovir (Valtrex, for example) can be used as an alternative to acyclovir to treat herpes infections and shingles. They require less frequent dosing and usually have similar or better results than acyclovir.

Side effects of famcyclovir are infrequent and may include headache, upset stomach, nausea and diarrhea. Side effects of valacyclovir are similar and also infrequent.

Penciclovir (Denavir, for example) cream is used to prevent recurring herpes sores (cold sores and fever blisters) on the lips. It may be especially helpful for people whose immune systems aren't functioning adequately, such as those who have HIV or AIDS.

Side effects of penciclovir are uncommon, but may include a headache or irritation at the application site.

Amantadine, rimantadine, zanamivir and oseltamivir
Amantadine (Symmetrel, for example) and rimantadine (Flumadine, for example) are used to treat influenza type A. When taken before exposure to the virus and continued throughout the period of exposure, these medications are 70 to 90 percent effective in preventing influenza type A. If taken within 48 hours of developing symptoms, they can also help treat influenza.

Side effects may include:

nausea
insomnia
dizziness, lightheadedness or faintness
nervousness or anxiety
behavioral changes
delirium
hallucinations
seizures
agitation
blurred vision
trouble sleeping
Zanamivir (Relenza, for example) and oseltamivir (Tamiflu, for example) can help reduce the length and severity of influenza types A and B when taken within 48 hours of developing symptoms. Oseltamivir may also be taken to prevent both types of influenza.

The most common side effects for zanamivir, which is inhaled, are nasal and throat discomfort. People who have asthma may experience breathing difficulty. Oseltamivir, which is taken orally, can cause nausea and vomiting.

Interferons
Healthy cells naturally produce interferons when they're invaded by viruses. Without bothering the healthy cells, the interferons stop virus reproduction. A variety of synthetic interferons are designed to fight certain viruses. The common alpha interferon, for example, is used to treat hepatitis B and C and genital warts. It also has the ability to prevent the development, growth or proliferation of malignant cells, making it useful in the treatment of certain types of cancer.

Side effects of alpha interferon may include:

joint, muscle and back pain
fever
chills
fatigue
appetite loss
stomach pain or diarrhea
skin rash
dry skin
itching
Ribavirin
Ribavirin (Rebetol or Virazole, for example) is used in combination with alpha interferon to treat chronic hepatitis C. In some children, an aerosol form of ribavirin is used to treat severe respiratory infection caused by the respiratory syncytial virus (RSV). It's also used to treat Lassa fever and hemorrhagic fevers, such as hantavirus.

Side effects of ribavirin may include:

nasal stuffiness
cough
rash
itching
anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron)
breathing difficulty in people who have asthma or a similar illness
Zidovudine
Zidovudine helps prevent HIV (the virus that causes AIDS) from spreading in the body. This drug can help people infected with the virus live longer, as well as ease the symptoms of advanced AIDS.

When used to treat AIDS, side effects may include:

nausea
vomiting
muscle pain
headaches
anxiety
confusion
anemia due to bone marrow suppression that decreases production of red blood cells
Combivir
Combivir, a combination of the medications zidovudine and lamivudine. is another medication used to treat HIV infections. It can help people infected with the virus live longer, as well as ease the symptoms of advanced AIDS. Combination therapies such as combivir may better control an HIV infection than treatment with one medication.

Side effects may include:

pancreatitis (inflammation of the pancreas)
neutropenia (a condition marked by a decreased number of a certain type of white blood cells that help protect against infections)
neuropathy (inflammation or degeneration of nerves)
anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron)
nausea
vomiting
muscle pain
headaches
anxiety
confusion