Since publication of our recent article on antiviral drugs for influenza, increased levels of resistance to oseltamivir (Tamiflu) have been detected in influenza A H1N1 strains.

Antiviral drugs can be used to control institutional influenza outbreaks and for prophylaxis of influenza exposures that occur before or less than 2 weeks after vaccination with inactivated vaccine, or in years when circulating strains differ from those included in the vaccine. They can also be used for early treatment of patients with influenza.

Our article on Antiviral Drugs for Prophylaxis and Treatment of Influenza (Med Lett Drugs Ther 2005;47:93) mentioned possible use of amantadine (Symmetrel, and others) and rimantadine (Flumadine, and others), but warned that the incidence of resistance has increased substantially. The CDC recently issued a Health Alert (www.cdc.gov) saying that current evidence indicates that a high proportion of circulating influenza A viruses in the US are now resistant to amantadine and rimantadine and they should not be used for this indication, at least this year. Click here to go to this update article.