What is Antiviral drug?
[[Virus]]es are the ultimate expression of [[parasitism]]. They not only take nutrition from the host cell but also direct it metabolic machinery to synthesize new virus particles. viral [[chemotherapy]] was considered impossible, as it would require interference with cellular metabolism in the host. ==Classification== 1. Anti-Herpes virus : idoxurudine, trifluridine, Acyclovir, valacyclovir, Famciclovir, Ganciclovir, Valganciclovir, Cidofovir, Foscarnet, Fomivirsen 2. Anti-Influenza virus: Amantadine, rimantadine, Oseltamivir, Zanamivir 3. Anti-Hepatitis virus/nonselective antiviral drugs Primarily for hepatitis B: Lamivudine, Adefovir dipivoxil, Tenofovir Primarily for [[hepatitis C]]: Ribavirin, Interferon α 4. Anti retrovirus: (A) neucleoside rivers transcriptas inhibitor: Zidovudine Didanosine, Stavudine, lamivudine, Abacavir, Emtricitabine, Tenofovir (B) nonnucleoside [[reverse transcriptase]] inhibitors (NNRTIs): Nevirapine, Efavirenz, Delavirdine (C) Protease inhibitors: Ritonavir, Atazanavir, Indinavir, Nelfinavir, Saquinavir, Amprenavir (D) Entry (Fusion) inhibitor: Enfuvirtide (E) CCR5 receptor inhibitor: Maraviroc (F) Integrase inhibitor: Raltegravir == Acyclovir == This deoxiguanosine analogue antiviral drug requires a virus specific enzyme for conversion to the active metabolite that inhibits DNA synthesis and viral replication. Acyclovir is taken by the virus infected cells. Because of selective generation of the active inhibitor in the virus infected cell and its greater inhibitory effect on viral DNA synthesis, acyclovir has low toxicity for host cells: a several hundred-fold chemotherapeutic index has been noted. === Pharmacokinetics === Only about 20% of an oral dose of acyclovir is absorbed. It is little plasma protein bound and is widely distributed attaining CSF concentration that is 50% of plasma concentration. After topical application, it penetrates cornea well. Acyclovir is primarily excreted unchanged in urine, both by glomerular filtration and tubular secretion; plasma t