11. ANTIVIRAL AGENTS & ANTI AIDS AGENTS

Antiviral agents are medicines used to prevent or treat infections caused by viruses. Unlike bacteria, viruses cannot reproduce on their own. They enter a host cell, use the host machinery to replicate, and then spread. Because of this, antiviral drugs are designed to block different steps of viral replication without harming the human host cell.

Classification of Viruses

Viruses can be broadly classified based on:

  • Type of genetic material (DNA or RNA)
  • Shape of the virus
  • Presence or absence of an envelope
  • Mode of replication

Virus Replication Cycle

Viruses generally follow a common pattern of replication:

  1. Attachment – Virus attaches to a host cell.
  2. Penetration – Viral material enters the cell.
  3. Uncoating – Viral genetic material is released.
  4. Replication – The virus uses the host machinery to make new viral components.
  5. Assembly – New viral particles are formed.
  6. Release – The new viruses exit the host cell to infect more cells.

Diseases Caused by Viruses

  • Influenza
  • Herpes infections
  • Hepatitis
  • Measles, mumps
  • HIV/AIDS

What Are Antiviral Agents?

Antiviral drugs work by blocking key steps in the viral life cycle. They may prevent the virus from entering cells, stop viral DNA/RNA synthesis, or prevent new viruses from being released. Most antivirals are specific to a particular virus.

Classification of Antiviral Drugs

Antiviral agents are commonly grouped as:

  • Anti-influenza drugs
  • Anti-herpes drugs
  • Anti-retroviral drugs (used in HIV/AIDS)
  • Non-selective antiviral agents

1. Anti-Influenza Viral Drugs

These drugs help prevent or treat influenza infections. They typically act by blocking viral uncoating or inhibiting neuraminidase enzymes needed for viral release. Examples include:

  • Amantadine
  • Rimantadine
  • Oseltamivir
  • Zanamivir

2. Anti-Herpes Viral Drugs

Herpes infections include cold sores, genital herpes, and herpes zoster. Drugs in this group usually inhibit viral DNA synthesis.

  • Acyclovir
  • Valacyclovir
  • Famciclovir
  • Ganciclovir

These drugs often act as nucleoside analogues, stopping viral DNA chain elongation.

3. Anti-Retroviral Drugs (HIV/AIDS Therapy)

HIV is a retrovirus that uses reverse transcriptase, integrase, and protease enzymes to replicate. Anti-retroviral therapy (ART) combines multiple drugs to control viral load and prevent resistance.

Major Classes of Anti-HIV Drugs

  • NRTIs – Nucleoside Reverse Transcriptase Inhibitors (e.g., Zidovudine, Lamivudine)
  • NNRTIs – Non-Nucleoside Reverse Transcriptase Inhibitors (e.g., Nevirapine, Efavirenz)
  • Protease Inhibitors – Block viral protein processing (e.g., Ritonavir, Saquinavir)
  • Integrase Inhibitors – Block viral DNA integration (e.g., Raltegravir)
  • Fusion/Entry Inhibitors – Prevent viral entry (e.g., Enfuvirtide)

4. Non-Selective Antiviral Agents

These drugs exhibit activity against a wide range of viruses. They may interfere with viral nucleic acid synthesis or inhibit viral enzymes. Examples include:

  • Ribavirin
  • Interferons

Detailed Notes:

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