Current status of amantadine and rimantadine as anti-influenza-A agents: memorandum from a WHO meeting

Amantadine (1-adamantanamine hydrochloride), an anti-influenza drug, effectively inhibits the replication of all human subtypes of influenza A virus (H1N1, H2N2 and H3N2) both in laboratory studies and in a variety of clinical situations in young and old persons. So far, it has been used on a relatively limited scale by community and hospital clinicians, partly because of concern over mild side-effects in approximately 6% of persons. The related compound, rimantadine (alpha-methyl-1-adamantane-methylamine hydrochloride), shows comparable antiviral activity with few or no side-effects. Although the mode of antiviral action is considered to be similar, the two drugs differ in their metabolic and pharmacological properties.Both amantadine and rimantadine have therapeutic uses and shorten the duration of influenza-A-induced fever, malaise, and virus shedding. A dosage of 200 mg of either drug for a 3-5-day period is effective but treatment has to commence on the first day of symptoms. Prophylaxis, particularly using rimantadine, could be usefully initiated in elderly and other high-risk individuals living in institutions and in the general community.