Safety of prolonged administration of rimantadine hydrochloride in the prophylaxis of influenza A virus infections in nursing homes.

We evaluated the safety of rimantadine hydrochloride (RH) prophylaxis in a double-blind, placebo-controlled trial in three nursing homes during a community epidemic of influenza A (H3N2). Although daily monitoring of the 35 participants revealed an association between RH administration (100 mg twice a day) and the development of nausea and anxiety (P less than 0.05), these and other potential side effects were transient and were rarely considered to be clinically significant. Serum RH levels measured at the end of the trial (mean, 1,159 ng/ml) were nearly three times higher than those measured previously in younger individuals, suggesting that lower dosages may be indicated for the elderly.