The World Health Organization (WHO) announced that despite research indicating that in some people influenza viruses can become resistant to Tamiflu, it remains its "drug of choice" for protection against bird flu and in case of a human flu pandemic.

Following the Japanese report that stated resistance to Tamiflu was more common than previously thought, WHO representatives did call for more information regarding the medication, which is produced by Switzerland's Roche. Oseltamivir, Tamiflu's active ingredient, is a neuraminidase inhibitor. It works by blocking the action of viral enzymes.

Researchers questioned the popular drug's use in a major pandemic, which experts fear could break out if the bird flu virus, now endemic in Asia, jumps to infect humans. Tamiflu was used earlier this year to help protect Asian workers culling chickens infected with bird flu.

Japanese researchers analyzed samples from 50 children who took the drug, and they found that flu viruses mutated to resist the medicine in 18 percent of the patients. In fact, resistant strains of the flu viruses were detected as early as four days after the start of treatment and on each successive day of the study.

WHO representatives acknowledged that the study was important but was done on a small scale.

Experts also said that the research done in Japan was done under a different treatment schedule. The study's patients were given less of the drug for less time than WHO recommends.

WHO representatives concluded that neuraminidase inhibitors still will be the top choice for the beginning stages of a pandemic until more extensive research can be done. They said Tamiflu has been "very important in drug treatment of avian flu in humans or influenza in general."

MSNBC, August 27, 2004