Antiviral drug

An antiviral drug, or antiviral agent, is a compound that interfers with the replication cycle of viruses. They can be divided into three non-exclusive categories: protease inhibitors, anti-metabolites and reverse transcriptase inhibitors, based on the ways in which they disrupt viral replication cycles. While antiviral drugs are intended for systemic use by ingestion or injection of the drug, virucides are used exclusively on objects and surfaces and, when possible, topically. Antiviral drugs are used extensively to treat HIV, hepatitis C, herpes and other devastating viruses. The protease inhibitor Atazanavir, popularly known as AZT, was the first widely used treatment for HIV.

Protease inhibitors, as the name suggests, inhibit the function of protease enzymes created by viruses. The DNA or RNA in viruses are coded to produce large polyproteins, which need to be cleaved into smaller functional proteins by viral proteases before infectious, mature virus particles can be formed. For example, West Nile virus and the Dengue fever virus produce a single polyprotein that must be cleaved into ten separate proteins. The antiviral drugs amprenavir, atazanavir, indinavir, nelfinavir, ritonavir, saquinavir and tipranavir are protease inhibitors.

Anti-metabolites are chemicals that mimic natural biochemical building blocks, and most often are analogs of the nucleotides used to make DNA and RNA. Anti-metabolites act as DNA or RNA chain terminators during the replication or translation of viral DNA or RNA. Often, the drugs are missing one of the necessary linkage groups, such as a 3'- or 5'-hydroxyl group in the sugar, sothat the drug gets incorporated into new viral RNA or DNA, but the next nucleotide base cannot be added because a linkage group is missing. Anti-metabolites also bind competitively with genuine metabolites in the active sites of the polymerases that create viral nucleic acids, and thus also slow down production of viral nucleic acids by clogging up the polymerases.

Many of the anti-metabolites are also reverse transcriptase inhibitors (RTIs). They inhibit the reverse transcriptase enzymes by binding to them either irreversibly by forming covalent linkages, or in competition with natural biochemicals. This class of drugs stops the conversion of viral RNA into DNA.

antimetabolites and RT inhibitors

• Abacavir - a powerful nucleoside analog reverse transcriptase inhibitor used to treat HIV and AIDS.

• Adefovir Dipivoxil - nucleotide analog reverse transcriptase inhibitor (ntRTI) hepatitis B treatment.

• Cidofovir - an viral DNA synthase inhibitor treats cytomegalovirus (CMV) retinitis.

• Delavirdine - A non-nucleoside reverse transcriptase (RT) inhibitor active against HIV-1.

• Didanosine - a dideoxynucleoside prevents phosphodiester bonds; it is an inhibitor of HIV replication.

• Emtricitabine - a cytidine analog, RT inhibitor for treatment of HIV.

• Entecavir - a guanosine analog for treatment of hepatitis B.

• Efavirenz - a non-nucleoside reverse transcriptase inhibitor (NNRTI)used to treat HIV.

• Famciclovir - a guanine analogue, treats herpesviruses, mostly for shingles.

• Foscarnet - inorganic pyrophosphate analog treats CMV retinitis, herpesviruses, and HIV.

• Ganciclovir - an acyclovir analog inhibitor of Herpesviruses including cytomegalovirus.

• Idoxuridine - a deoxyuridine analog that inhibits viral DNA synthesis.

• Lamivudine - An RT inhibitor, zalcitabine analog used to treat HIV disease

• Nevirapine - a non-nucleoside reverse transcriptase inhibitor used to treate HIV/AIDS

• Oseltamivir (Tamaflu) - inhibits neuraminidase in the treatment of influenza infections.

• Penciclovir - a guanine analogue used to treat various herpesviruses

• Ribavirin - a nucleoside antimetabolite used against both RNA and DNA viruses.

• Rimantadine - a cyclic amine derivate of adamantane, inhibits replication of influenza A, but not B.

• Stavudine - A dideoxynucleoside analog, inhibits reverse transcriptase in HIV treatment.

• Tenofovir - a nucleoside analog, reverse transcriptase inhibitor (nRTI),

• Vidarabine - purine nucleoside analogue for the treatment of chickenpox (varicella) and herpes viruses

• Zalcitabine - a dideoxynucleoside, prevents phosphodiester bonds, a potent inhibitor of HIV replication.

• Zanamivir - a guanido-neuraminic acid used to inhibit neuraminidase, inhibits influenza.

• Zidovudine - A dideoxynucleoside, prevents phosphodiester bonds, a potent inhibitor of HIV replication.

External Links

Drug Bank at http://www.drugbank.ca/cat_browse.htm#subC10