- Antiviral agents are medications used to treat viral infections by either inhibiting viral replication or modulating the host’s immune response.
- These agents can be classified based on their target viruses or mode of action.
Classification of Antiviral Agents
1. Influenza A Virus Inhibitors
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- These agents inhibit viral replication by blocking the M2 protein, an ion channel essential for the viral lifecycle.
- They are effective primarily against influenza A viruses.
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Examples:
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2. Anti-Herpes Virus Agents
- These agents work by inhibiting viral DNA synthesis in herpes viruses.
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Examples:
- Idoxuridine Trifluoride (used topically for herpetic keratitis)
- Acyclovir
- Ganciclovir
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Mechanism of Action:
- Idoxuridine is incorporated into viral DNA, disrupting replication.
- Acyclovir & Ganciclovir are nucleoside analogs that, once phosphorylated, act as competitive inhibitors of viral DNA polymerase and function as chain terminators.
3. Reverse Transcriptase Inhibitors (Anti-HIV Agents)
- These drugs inhibit the reverse transcriptase enzyme, which is critical in the lifecycle of retroviruses like HIV.
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Examples:
- Nucleoside Reverse Transcriptase Inhibitors (NRTIs):
- Zidovudine
- Didanosine
- Zalcitabine
- Lamivudine
(Incorporated into viral DNA, causing chain termination.)
- Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs):
- Loviride
- Delavirdine
(Bind to reverse transcriptase, inducing conformational changes that inhibit activity.)
- Nucleoside Reverse Transcriptase Inhibitors (NRTIs):
4. Protease Inhibitors (Anti-HIV Agents)
- These agents inhibit HIV protease, preventing the cleavage of viral polyproteins into functional proteins, which is essential for viral maturation.
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Examples:
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5. Broad-Spectrum Antiviral Agents
- These agents exhibit antiviral activity against a wide range of RNA and DNA viruses.
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Example:
- Ribavirin (Believed to inhibit viral RNA synthesis and modulate the host’s immune response.)
