More than 99 percent of the seasonal H1N1 viruses have shown resistance to Tamiflu, which has been considered one of the first-line drugs for this strain in prior years.

A Centers for Disease Control and Prevention advisory committee has found drug resistance in all but one of the anti-viral drugs used for influenza-like illness, “whether the infection is caused by a seasonal virus or the pandemic H1N1 virus.” (Emphasis added)

Since spring, SmithGlaxoKline, manufacturer of Relenza, has reported “ample” supplies of the drug through company statements and news stories.

What Can You Do?

• Report flu-like symptoms to your doctor right away to determine what is appropriate for you.
  
• If your doctor tells you to take antiviral medication, you should start it right away.
• According to the CDC advisory panel, only one medication is effective with this year’s influenza-like illnesses. The drug brand name is Relenza.
  
• Consult the CDC Swine Flu section on its Home Page, which has advice for patients and those who care for them at home.
  

Medpage Today

“Zanamivir (Relenza), a neuraminidase inhibitor, should be the preferred treatment for patients with influenza-like illness, whether infection is caused by a seasonal virus or the pandemic H1N1 virus, an advisory committee to the CDC said. (Emphasis added)

“Even if laboratory tests are negative but flu is still suspected, zanamivir should be used when antiviral treatment is considered, the Advisory Committee on Immunization Practices agreed here.

“Oseltamivir (Tamiflu), another neuraminidase inhibitor, could be used in case of a test that’s positive for seasonal influenza A H3N2 or B, or for pandemic influenza A H1N1, although more than 99% of the seasonal H1N1 viruses were resistant to the drug, the committee noted.

“The recommendations were based on testing for antiviral resistance, which found that all strains recently isolated, including the new H1N1, were susceptible to zanamivir.

“Researchers found varying levels of resistance to the adamantanes, rimantadine and amantadine.”

“The recommendations, which will be published in an upcoming issue of Morbidity and Mortality Weekly Report, stressed that treatment should start as soon as possible for patients needing treatment.” ( Emphasis added)

Source: Medpage Today, June 29, 2009

Citation: CDC Morbidity and Mortality Weekly Report, Publication Pending.