Triazavirin is a nucleoside analogue of nucleic acid and an antiviral agent. Triazavirin works by inhibiting the synthesis of viral RNA and DNA and replication of genomic fragments. Triazavirin is also an effective protective agent on the transmission stage of influenza.IC50 & Target: Nucleoside analogue; Influenza virusIn Vitro: The efficacy of Triazavirin against the tick-borne encephalitis virus is estimated in the sensitive cell culture. In a concentration of 128 mcg/mL Triazavirin is shown active in inhibition of the tick-borne encephalitis virus reproduction (strain Sofiin) by accumulation in the SKEV cell culture[2].In Vivo: The therapeutic efficacy Triazavirin against experimental Forest-Spring encephalitis on albino mice is studied. The results shows that in high doses (200-400 mg/kg) Triazavirin moderately protects the infected animals. A significant increase of the animal lifespan in the test groups (from 4.1 to 4.8 days) and a statistically valid decrease of the virus accumulation in the target organ are observed.