Antiviral Drugs

ANTIVIRAL DRUGS

Viruses are the ultimate expression of parasitism: they not only take nutrition from the host cell but also direct its metabolic machinery to synthesize new virus particles. Viral chemotherapy, therefore, is difficult, as it would require interference with cellular metabolism in the host. However, virus directed enzymes have been identified in the infected cell and some viruses have few enzymes of their own which may have higher affinities for some antimetabolites or inhibitors than the regular cellular enzymes. Drugs could also target virus specific steps like cell penetration, uncoating, reverse transcription, virus assembly or maturation. Another stumbling block is that in majority of acute infections viral replication is already at its peak when symptoms appear. To be effective, therefore, therapy has to be started in the incubation period, i.e. has to be prophylactic.

Classification

1. Anti-Herpes virus

Idoxuridine, Acyclovir, Valacyclovir, Famciclovir, Ganciclovir*, Foscarnet*

2. Anti-Retrovirus

Nucleoside Reverse Transcriptase Inhibitors (NRTIS): Zidovudine (AZT), Didanosine, Zalcitabine*, Stavudine, Lamivudine, Abacavir

Nonnucleoside Reverse Transcriptase Inhibitors (NNRTIS): Nevirapine, Efavirenz, Delavirdine*

Protease Inhibitors: Ritonavir, Indinavir, Nelfinavir, Saquinavir, Amprenavir*, Lopinavir

3. Anti-Influenza Virus

Amantadine, Rimantadine*

4. Nonselective Antiviral Drugs

Ribavirin, Lamivudine, Adefovir dipivoxil, Interferon α

* Not yet marketed in India.