Antiviral Agents

Classes of medication used specifically for treating viral infections are termed as antiviral agents. In other words, these are medicines/drugs that treat viral infections and inhibit their spread. They act against virus by preventing the replication of the genome, blocking entry to host cells, inhibiting viral protein synthesis and viral assembly.

Antibiotics normally used to treat bacterial disease cannot be used to inactivate viruses because viruses do not perform the biochemical functions that are intervened by antibiotics. For example, penicillin is used to interrupt the synthesis of the bacterial cell wall, but virus doesn’t possess cell wall.

Most of virus inhibiting drugs work only when virus is replicating and are used for specific viral infections (i.e. narrow spectrum) while a broad-spectrum antiviral is effective against a wide range of viruses. They do not destroy their target pathogen but, inhibit their development.

Antiviral agentss can be of various classes such as:

  • Antiviral drugs
  • Interferon
  • Viral Vaccine
  • Virus inactivation


Antiviral drugs


There are several nucleotide analog drugs that interfere with viral replication. E.g. Acyclovir is used against herpes viruses, this drug prevents the synthesis of DNA during viral replication. Azidothymidine (AZT) used for patients with HIV infection also prevents the synthesis of DNA. Similarly, ganciclovir is used against cytomegaloviruses, and amantadine is useful against influenza viruses.

Interferon, a naturally produced antiviral agent approved for certain uses, is a group of proteins produced by host cells after they have been infected by viruses. They do not protect the host cell, but they do provide protection to neighboring cells against viral replication. These can be produced by genetic engineering methods.

Viral vaccines: Protection against viral disease can be rendered by using a viral vaccine. Viral vaccines can be composed of inactivated or attenuated viruses.


Virus Vaccine


  • Inactivated viruses(dead viruses) are unable to replicate in host cells because of some chemical or physical treatment. Salk vaccine against polio and the yellow fever vaccine are examples.
  • Attenuated viruses(live viruses) are weakened viruses that replicate at a very slow rate in host cells and generally do not produce any symptoms of disease when inoculated to humans. E.g. Hepatitis B vaccine. Attenuated viruses are used in the Sabin polio vaccine and in the vaccines against measles and rubella.

The most contemporary vaccines are composed of viral proteins produced by genetic engineering methods.

Viral inactivation: Virus particles are composed of nucleic acid, protein, and in some cases, a lipid envelope. As such, the viruses are susceptible to normal inactivation by chemical substances that react with any of these organic compounds. Such things as chlorine, iodine, phenol, detergents, and heavy metals rapidly inactivate viruses.


Viral Inactivation


In addition, viruses are destroyed by heating methods used for other microorganisms, and they are very susceptible to the effects of ultraviolet light. Filters can be used to remove viruses from fluids so long as the filter pores are small enough to trap viral particles.

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