Amantadine and rimantadine are the specific antiviral agents available for treatment of influenza. These drugs are effective against influenza A virus but not against influenza B virus.
These drugs when given within 1–2 days of the onset of illness, reduce severity of the disease and also hasten the disappearance of fever and other symptoms. The drugs are recommended for prevention of influenza in elderly unimmunized population in whom the influenza can cause a life-threatening infection. Emergence of viral resistance can occur during treatment.
Zanamivir (Relenza) and oseltamivir (Tamiflu) are newer drugs for treatment of influenza and are effective against both influenza A and B viruses. These are the NA inhibitors, which act by inhibiting the release of viruses from infected cells. These drugs also prevent the spread of virus from one cell to another. Relenza is used in the form of nasal spray, whereas Tamiflu is given orally.