Antiviral agents are medications used to treat viral infections by inhibiting viral replication or by modulating the host's immune response.
They can be classified based on their target viruses or their mode of action.
Here's a general classification of antiviral agents based on the viruses they target:
1. Influenza A Virus Inhibitors:
·Amantadine Hydrochloride
Rimantadine Hydrochloride
These agents inhibit viral replication by blocking the function of the M2 protein, an ion channel necessary for the viral lifecycle.
They are effective primarily against influenza A viruses.
2. Anti-Herpes Virus Agents:
Idoxuridine Trifluoride (although it is mainly used topically for herpetic keratitis, not systemic infection)
Acyclovir*
Ganciclovir
These agents work by inhibiting viral DNA synthesis in herpes viruses.
Idoxuridine is incorporated into viral DNA in place of thymidine, disrupting the viral replication process.
Acyclovir and ganciclovir are nucleoside analogs that, once phosphorylated within the cell, act as competitive inhibitors of the viral DNA polymerase and as chain terminators.
3. Reverse Transcriptase Inhibitors (Anti-HIV Agents):
Zidovudine
Didanosine
Zalcitabine
Lamivudine
Loviride (non-nucleoside reverse transcriptase inhibitor)
Delavirdine (non-nucleoside reverse transcriptase inhibitor)
These drugs inhibit the reverse transcriptase enzyme, a critical component in the lifecycle of retroviruses such as HIV.
The first four are nucleoside reverse transcriptase inhibitors (NRTIs) and work by being incorporated into the viral DNA and terminating the chain.
The latter two are non-nucleoside reverse transcriptase inhibitors (NNRTIs), which bind to a different site on the same enzyme, inducing a conformational change and thus inhibiting its activity.
4. Protease Inhibitors (Anti-HIV Agents):
Saquinavir
Indinavir
Ritonavir
These agents inhibit the protease enzyme in HIV, preventing the cleavage of the virus's polyprotein precursors into functional proteins, which is a necessary step in the virus's lifecycle.
5. Broad-Spectrum Antiviral:
Ribavirin
Ribavirin has broad-spectrum antiviral activity against a range of RNA and DNA viruses.
Its exact mechanism of action is not fully understood, but it is believed to work by inhibiting viral RNA synthesis and modifying the host's immune response.