Amantadine and rimantadine for the prevention of influenza A.

Influenza is a leading cause of morbidity and mortality in the United States, particularly among persons with cardiac and/or pulmonary disease and those over age 65. Vaccine is effective but not completely protective. Prophylaxis with one of the antivirals, amantadine or rimantadine, has proven efficacy against influenza A virus infections. It should be considered for high-risk patients both in the community and in health care facilities where these subjects are concentrated. Prophylaxis also has potential benefit in the home when an index case of acute influenza has been identified. The dose of drug that is most appropriate is under study. Based on observations made in young patients, it is hoped that rimantadine will be better tolerated by the elderly than has been the case with amantadine. Assessment of efficacy in outbreaks caused by viruses of different antigenic make up and elevation of the significance of drug resistance will be important in judging the true value of prophylaxis of influenza with either of these antivirals.