Friday, May 25, 2007

Why They Are Used

Why They Are Used

The main area where anti-viral drugs are helpful is in the treatment of various conditions caused by the herpes virus: cold sores, encephalitis, genital herpes, chickenpox, and shingles.

Some drugs are applied topically to treat cold sores, herpes, eye infections, and genital herpes. They can reduce the severity and duration of an outbreak but do not eliminate the infection permanently. Other anti-viral drugs are given by mouth or, under exceptional circumstances, by injection to prevent chickenpox or severe, recurrent attacks of the herpes virus infections in those who are already weakened by other conditions.

Anti-viral agents are also given to prevent influenza A, as is Amantadine, a drug for Parkinsonism that also has anti­viral properties.

The interferons are proteins produced by the body and involved in the immune response and cell function. Interferon alpha and beta have recently been shown to be effective in reducing disease activity in people infected with hepatitis B and hepatitis C. Further research into the anti-viral activity of these agents is under way, including their use in the treatment of central nervous system conditions, such as multiple sclerosis.

AIDS (acquired immune deficiency syndrome) is caused by infection with the human immuno deficiency virus (HIV), which reduces the body's resistance to infection by other viruses, bacteria and protozoa, and to some types of cancer.

How They Work

Some anti-viral drugs, such as Idoxuridine, act by altering the cell's genetic material (DNA) so that the virus cannot use it to multiply. Other drugs stop multiplication of viruses by blocking enzyme activity within the host cell. Halting multiplication prevents the virus from spreading to uninfected cells and improves symptoms rapidly. However, in herpes infections, it does not eradicate the virus from the body. Infection may therefore flare up on another occasion.

Amantadine has a different action : it stops the virus from entering cells. It is therefore most effective when given prophylactically, before the infection has spread widely.

How They Affect You

Topical anti-viral drugs usully start to act at once. Provided that the treatment is applied early enough, an outbreak of herpes can be cut short. Symptoms usually clear up within two to four days. Anti-viral ointments may cause irritation and redness. Anti-viral drugs given by mouth or injection can occasionally cause nausea and dizziness.

Risks and Special Precautions

Because some of these drugs may affect the kidneys adversely, they are prescribed with caution for people with reduced kidney function. Some anti-viral drugs can adversely affect the activity of normal body cells, particularly those in the bone marrow. Idoxuridine is, for this reason, available only for topical application.

Common Drugs

Aciclovir, Amantadine Cidofovir, Famciclovir, Foscarnet, Ganciclovir, Idoxuridine, Inosine pranobex, Interferon, Penciclovir, Tribavirin, Valaciclovir, Zanamivir.


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