Antiviral Drugs

See also the following individual entries:

Acyclovir (Acycloguanosine) Amantadine hydrochloride Cidofovir

Delavirdine mesylate

Didanosine (ddI, Dideoxyinosine)

Famciclovir

Indinavir sulfate

Lamivudine

Lamivudine and Zidovudine

Nelfinavir mesylate

Nevirapine

Penciclovir

Ritonavir

Saquinavir mesylate Zalcitabine

Zidovudine (Azidothymidine, AZT)

Action/Kinetics: To maintain their growth and reproduce, viruses must enter living cells. Thus, it is difficult to find a drug that is specific for the virus and that does not interfere with the function of the host cell. However, there are enzymes and replicative mechanisms that are unique to viruses and an increasing number of drugs with specific antiviral activity have been developed. The antiviral drugs currently marketed act by one of the following mechanisms:

1. Inhibition of enzymes required for DNA synthesis. Example: Idoxuri-dine.

2. Inhibition of viral nucleic acid synthesis by interacting directly with herpes virus DNA polymerase or HIV reverse transcriptase. Example: Foscarnet.

3. Inhibition of viral DNA synthesis. Examples: Acyclovir, Cidofovir, Di-

danosine, Famciclovir, Ganciclovir, Penciclovir, Trifluridine, Valacyclo-vir, Vidarabine.

4. Prevent penetration of the virus into cells by inhibiting uncoating of the RNA virus. Examples: Amanta-dine, Rimantadine.

5. Protease inhibitors resulting in release of immature, noninfectious viral particles. Examples: Indinavir, Riton-avir, Nelfinavir, Saquinavir.

6. Inhibition of reverse transcriptase resulting in inhibition of replication of the virus. Examples: Lamivudine, Nevirapine, Stavudine, Zalcitabine, Zidovudine. It is becoming increasingly common to combine two antiviral drugs that have different mechanisms of action in order to treat HIV infections.

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