Amantadine is the first antiviral drug for human which was developed by duPont chemical company in 1964. Amantadine causes a selective, dose-related effectiveness of type A influenza virus and cost performance is very high. Amantadine should be given within 48 hours from onset of influenza. Daily doses should not exceed 150 mg in children, 200 mg in adults and less than 100 mg for renal insufficiency. The faulty point of amantadine is that influenza virus becomes easily resistant to the drug through aminoacids change of ionchannel of M2 protein. Fortunately resistant virus is less virulent and has short life in practical meaning. As rapid diagnostic kits are conveniently available for influenza, you should choice amantadine when the patient was positive for type A influenza by kit, especially neuraminidase inhibitor drugs became shortage.