One of the few drugs known to be effective against the potentially pandemic avian flu is the antiviral drug Tamiflu. But, a new report finds further evidence that some patients may develop a resistance to it.

The New England Journal of Medicine on Wednesday said two Vietnamese patients were treated with Tamiflu but resistant to it and died from the H5N1 avian flu virus.

Health experts are calling the development alarming.

Dr. Frederick Hayden from the University of Virginia School of Medicine in the U.S. said Tamiflu is the key drug that governments are stockpiling in case of a large-scale outbreak of avian flu.

"It's important to recognise there are real limitations in terms of the extent of the clinical benefits that should be expected," he said.

Dr. Charles Monto from the University of Michigan School of Public Health suggests that the doses doctors now consider ideal may be too little.

"We wouldn't expect Tamiflu alone to be able to cure people who have very severe disease. Number two, most of them were treated late," Monto said.

Experts said the deaths of the two bird flu patients in Vietnam are disturbing because they had received early and aggressive treatment with Tamiflu and had received the recommended doses.

(Source: CRIENGLISH.com)