Prevention, management, and control of influenza. Role of amantadine

Amantadine, an oral antiviral agent, is effective in the prophylaxis and treatment of all strains of influenza A, preventing 70 to 90 percent of both experimentally induced and natural infections. Although not a substitute for vaccination, prophylactic amantadine can be particularly helpful in high-risk groups, including those with cardiovascular and pulmonary diseases and those in chronic-care settings. Adjunctive administration to previously immunized high-risk persons enhances the vaccine's efficacy. If given to nonimmunized persons who are then vaccinated during an influenza out-break, it will protect them for the two to three weeks needed for vaccine-induced immunity to develop. If given to residents of a chronic-care facility early in an outbreak, it is helpful in controlling the outbreak. Used therapeutically within 48 hours of the onset of symptoms, amantadine will shorten influenza illness by up to 50 percent, reduce fever, and hasten the resumption of normal activities. Amantadine is particularly recommended for high-risk persons in whom influenza-like symptoms develop during a confirmed or suspected outbreak of influenza A.