New study urges docs to ditch flu drugs

Citing data showing that the prevalence of drug-resistant influenza strains increased sharply since last year, several researchers called for a moratorium on prescriptions for the most used antiviral influenza treatments on Feb. 1. The recommendation came in an article published in the Journal of the American Medical Association (JAMA) showing an eight-fold increase in drug resistance among flu strains. According to the researchers, who work at the US Centers for Disease Control (CDC), the incidence of drug-resistant strains of influenza in the United States had already risen precipitously over the past two years, from just under 2 percent of samples in 2004 to 11 percent last year. JAMA published the results of a study of 209 separate flu samples from the 2005-2006 flu season. The study found that 92 percent had developed some form of resistance to amantadine and rimantadine–marketed as Symmetrel and Flumadine, respectively–the drugs of choice for controlling flu outbreaks in hospitals. Doctors often prescribe the drugs to ameliorate acute flu symptoms in individual patients. The study, conducted by five CDC researchers, replicates an earlier government study of 120 flu isolates that found 91 percent had developed resistance to one or both of the leading medications. In a Jan. 14 statement, the CDC reported the results of the first study and advised doctors to stop prescribing the drugs. In an editorial accompanying the report, a doctor affiliated with the Sloan-Kettering Cancer Center in New York noted that much contemporary research points to the mis- and over-use of antiviral drugs as the main cause for the increase in drug-resistant flu strains. "Inappropriate use of anti-infectives invariably results in resistance," editorial author David M. Stock said. Echoing recommendations made by the study authors, Stock called for increased flu monitoring and better-regulated use of antiviral medicines worldwide. He concluded, "If antiviral use is curtailed, susceptible strains could emerge and [amantadine and rimantadine] could regain their utility against both epidemic and pandemic influenza." Drug-resistant flu strains have been much more common overseas, Reuters reported on Feb. 1. In China nearly three in four strains exhibited resistance last year, medical experts told the news service. There are no statistics available for this year. Though accurate numbers are hard to come by and some groups maintain that the pharmaceutical industry inflates the data, most medical experts believe that over a half a million people worldwide and tens of thousands in the US die annually from the flu.