The drugs amantadine and rimantadine can both help prevent and relieve the symptoms of influenza A in adults, but amantadine has more adverse effects.
The flu can be caused by many different viruses. One type is influenza A, with headaches, coughs and runny noses that can last for many days and lead to serious illnesses such as pneumonia. Amantadine and rimantadine are antiviral drugs. The review of trials found that both drugs are similarly helpful in relieving the symptoms of influenza A in adults, but only when there is a high probability that the cause of the flu is influenza A (a known epidemic, for example). It is likely that neither drug will interrupt the spread of influenza A and by treating symptoms may encourage viral spread in the community by people who are feeling better but are still infectious. Resistance of influenza viruses to amantadine is a serious worldwide problem as shown by recent surveys. Both drugs have adverse gastrointestinal (stomach and gut) effects, but amantadine can also have serious effects on the nervous system. They should only be used in an emergency when all other measures fail.