End of treatment and sustained response to peginterferon alfa-2a (40KD) (PEGASYS) plus ribavirin (RBV) (COPEGUS) and amantadine (AMA), and to induction therapy with interferon (IFN) alfa-2a (Roferon-A) plus RBV and AMA in IFN/RBV nonresponders with chronic hepatitis C (CHC).