Disclosed is a pharmaceutical composition comprising a pyrazine derivative represented by the general formula:[wherein R1 and R2 independently represent a hydrogen atom or a halogen atom； and R3 represents a hydrogen atom or an amino-protecting group] or a salt thereof and at least one neuraminidase inhibitor. The pharmaceutical composition is useful for a treatment including the treatment or prevention of influenza. Also disclosed is a method of using these components in combination. The method is useful for a treatment including the treatment or prevention of influenza.
