Antiviral drug is the term for a group of chemical compounds used to treat diseases caused by viruses. Antiviral drugs usually do not cure viral diseases but can shorten the duration of the disease and lessen the severity of symptoms. Many antiviral drugs, however, can cause side effects, such as anemia or kidney damage.
Many viral diseases can be prevented through the use of vaccines. But vaccines have not been developed for all viral diseases, and vaccines are not useful for treating people once they become ill. Other drugs, including antibiotics such as penicillin, have no effect on viruses.
Viruses use substances within the cells of living organisms, called host cells, to manufacture enzymes and other materials they need to reproduce. Antiviral drugs work by interfering with parts of the viral life cycle that are different from steps completed by the hosts. This allows drugs to attack viruses while not harming host cells. However, since viruses rely on substances made by hosts to carry out many steps in their life cycles, there are only a few viral materials that the drugs can target. Getting drugs into infected cells is also an obstacle. In spite of these difficulties, researchers have developed many successful antiviral drugs.
Many antiviral drugs are chemical compounds that bind to viral enzymes, changing the structure so the enzymes cannot be used by the viruses. The drugs bind only to viral enzymes, while enzymes used by the host cell are not impaired. The virus, however, cannot reproduce to infect other host cells. The progression of the disease is thus slowed or halted by the drugs.
The first antiviral drugs were developed in the 1960’s. One of the earliest, acyclovir, is widely used to treat infections of herpesviruses, a group of viruses that cause chickenpox, mononucleosis, shingles, and cold sores. This drug mimics a building block of the genetic material DNA (deoxyribonucleic acid) which herpesviruses need to reproduce. Viral enzymes mistakenly add this drug into a growing strand of DNA and stop its production. Acyclovir is given to patients by injection, as a pill, or in ointment applied to the skin. Other drugs, such as zanamivir, used to treat influenza, can be inhaled. Many antiviral drugs available today have been developed to treat HIV, the virus that causes AIDS.
Scientists are developing new antiviral drugs as they learn more about the structure and life cycle of viruses. Researchers analyze the chemical structure of viral enzymes and proteins. They use computers to design chemical compounds that will bind to the viruses without causing side effects in the host.
