Antiviral Drugs

A number of antiviral drugs are used today to treat influenza. Most work either by inhibiting the virus replication, or stimulating immune system and easing the symptoms. The former can be split into 2 main groups by their mechanism of action: M2 inhibitors and Neuraminidase inhibitors. M2 inhibitors (Rimantadine, Amantadine) have been successfully used to treat influenza A since the 70s; however, the number of influenza A strains resistant to these medications has risen significantly. Neuraminidase inhibitors (Oseltamivir, Zanamivir) became available in the end of the 90s. They are effective against influenza A and B, but require early administration, within 36–48 hours of the illness onset, to take effect. If the administration is delayed their efficacy decreases severely.

Nucleoside drugs — Ribavirin and its analogues — which inhibit viral RNA–polymerase activity, i.e. viral nucleic acid synthesis, see limited use because of their adverse effects. Nevertheless, nucleoside drugs show serious antiviral potential against influenza and other DNA and RNA viruses. Currently, RII is conducting phase II clinical trial of Triazavirin, a novel nucleoside drug, which showed lower toxicity compared to Ribavirin and high efficacy against avian influenza and other RNA viruses.

Another common Russian antiviral, Arbidol, was synthesized in the middle of the 90s. It works by inhibiting fusion between viral capsid and cell membrane of the target cell, preventing virus from entering the cell. The drug showed low toxicity, considerable efficacy and has low production value. It is affective against influenza A, B and some ARI agents.

Additionally, Russian healthcare promotes the use of interferons and interferon inductors as a prophylaxis and treatment of influenza. Interferons can selectively inhibit viral replication process without compromising cell metabolism. Genetically engineered recombinant compounds of interferon (Grippferon, Viferon, Reaferon) are widely used in medical practice. Interferon inductors include low–molecular synthetic compounds (Amixin, Cycloferon) and organic compounds (Kagocel), which were selected through years of careful screening. These preparations showed efficacy in treating and preventing variety of acute respiratory infections. Although the mechanism of action of interferons is not well understood and some influenza strains, e.g. H5N1 show resistance to interferon therapy, they still can be recommended as a prophylactic mean due to activation of interleukins, macrophages, strengthening of phagocytosis and other functions of non–specific organism protection.