Adverse Reactions to Amantadine Prophylaxis of Influenza in a Retirement Home

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Abstract
Controversy exists about the safety of following the recommendation of the Immunization Practice Committee of the Centers for Disease Control that nursing home residents be given amantadine prophylaxis during influenza outbreaks. This study was undertaken to define the incidence of adverse reactions to amantadine in the elderly and to identify risk factors for side effects. A retrospective cohort study. A retirement home which offered amantadine prophylaxis to its residents during a presumed influenza outbreak. Of the 96 elderly residents, 79 accepted the offer of amantadine prophylaxis. Attributable adverse health outcomes as assessed by chart review. 41% of the people receiving amantadine had attributable adverse reactions, of which 22% were classified as severe. Severe adverse reactions were associated with residence in the assisted living section of the facility (P = 0.002), a greater number of underlying diagnoses (P = 0.009), congestive heart failure (P = 0.02), and high serum creatinine (P = 0.02). A person with none of these risk factors had a 7% chance of having a severe adverse outcome compared to a 70% chance for someone with all four risk factors. The findings raise concern that the prophylactic administration of amantadine to all elderly residents of nursing and retirement homes may be associated with a high incidence of unacceptable reactions, particularly among less healthy residents.