text: Currently, there are two classes of antiviral drugs approved for the treatment and prophylaxis of influenza infections. They are the adamantanes and NAIs. The adamantanes only work on influenza A so since 2010 WHO recommended the usage of NAIs for treatment and prophylaxis of influenza A and B infections. In contrast to adamantanes, NAIs are less toxic and less prone to promote drug-resistant influenza. Moreover, they are effective against all neuraminidase subtypes and all strains of influenza. After the influenza pandemic in 2009, there has been great concern about viral resistance to NAIs. Influenza viruses that have reduced sensitivity to NAIs often contain mutation that affect the shape of the NA catalytic site and therefore reduce the binding ability of the inhibitors. The catalytic site of the NA has eight functional residues ( R118, D151, R152, R224, E276, R292, R371, and Y406) surrounded by eleven framework residues (E119, R156, W178, S179, D198, I222, E227, H274, E277, N294, and E425).