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Anti Viral Drugs

Viruses are the intracellular parasites that depend on synthetic processes of host cells. They cannot be grown on ordinary medium. Special microscopes are needed to visualize their structure, which consists of three main components:

1. Genome –genetic material consisting of DNA or RNA component but never both.

Most common are single stranded RNA and double stranded DNA viruses.

2. Surrounding capsid –proteinaceous in structure
3. Envelope –protein bilayer, not present in all viruses, those devoid are known as naked.

Additional to structural components, host cell surface receptors are present.

Glycoproteins are present for attachment to host.

Virus consisting of these main components is known as virion.

Virus Life Cycle

Series of processes facilitate entry of virus, which incorporates into nucleic acids, resulting in rapid replication. It damages human nucleic acid, producing toxic effects.

Antivirals are exclusively directed against viral nucleic acids and not humans, due to which chemoprophylaxis becomes difficult.

  1. Attachment to cell surface. Virus gets attached to host cell receptors.
  2. Once attached, structural proteins recognize.
  3. Binding of these two components lead to conformational changes.
  4. Lysoproteins are also recognized, fusion occurs.
  5. Penetration inside host cells takes place.
  6. Uncoating of virus occurs
  7. Once uncoating has occurred, genetic material is transcribed and translated within host nucleus
  8. Proteins are formed and budding of virus occurs.

Different antivirals target different steps of this life cycle.

Common Viruses

Main difference between DNA and RNA viruses is of site. RNA viruses utilize own mRNA and not of host. Their own polymerases synthesize essential mRNA.

DNA Viruses:

  • Pox virus
  • Herpes virus
  • Adeno virus
  • Papilloma virus

RNA Viruses:

  • Rubella virus
  • Arenavirus
  • Arboviruses
  • Orthomyxovirus
  • Paramyxovirus
  • Rhabdo virus
  • Picorna virus
  • Retro  virus

Antiviral Drugs Classification

1.  Drugs that inhibit uncoating of viral RNA 

  • Amantadine
  • Rimantadine
  • Gamma globulins

2. Drugs that inhibit viral nucleic acid synthesis (DNA Polymerase inhibitors)

3.   Drugs that inhibit late protein synthesis and processing             

  • Protease inhibitors

4.   Immunomodulators

  • Interferons

Therapeutic Classification

1      Agents to treat HSV & VZV infections (DNA – Polymerase Inhibitors)

2.     Agents to treat CMV (cytomegal0virus) Infections

3.     Agents to treat  Hemorrhagic  fevers (Dengue, Crimean congo,)

  • Ribavirin (with anti-hepatitis agents, INF, also effective in influenza)

4.   Agents to treat Influenza  infections

5.   Agents to treat human papilloma virus infections (genital warts)

  • Imiquiumod (topical )

6.    Agents to treat Bird Flue

  • Oseltamivir.
Antihepatitis agents

Hepatitis B

Hepatitis C

Anti-Retroviral Agents (for AIDS patient)

A. Nucleoside Reverse Transcriptase Inhibitors (NRTIs)

B. Nonnucleoside Reverse Transcriptase Inhibitors (NNRTIs)

C. Protease Inhibitors

D.   Fusion Inhibitors

E.  Integrase Inhibitors

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DNA Polymerase Inhibitors

Anti Influenza Agents

Anti Retroviral Agents (HAART) -Highly Active Antiretroviral Therapy

Anti Hepatitis Drugs

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