According to the report of Japanese scientists, there are signs of resistance to two popular antiviral medications widely used to fight the flu strain called influenza B.
The two medications, zanamivir (Relenza) and oseltamivir (Tamiflu), have been successful in the treatment of the flu and are frequently used, especially in Japan, according to the report in the April 4 issue of the Journal of the American Medical Association.
Resistance through overuse
"We are worried about occurring resistance patterns through overuse of these medications," explained Dr Marc Siegel, a clinical associate professor of medicine at New York University School of Medicine. "This research is another caution to the overuse of a medicine based on fear."
These medications are designed to be taken by patients who have just fallen ill with the flu or are in close relation with somebody suffering the flu, Siegel explained. "These medicines ought not to be given when you hear on the news that miles away someone has the flu," he added.
There has been evidence of influenza A virus that is resistant to Tamiflu, however information concerning influenza B viruses has been restricted. According to the scientists, influenza B viruses constitute the cause of annual outbreaks of flu.
In the research, Dr Shuji Hatakeyama, of the University of Tokyo, and the team analyzed the cases of influenza B resulting from decreased sensitivity to these medicines in Japan.
In 2004-2005, there was the most important outbreak of an influenza B in Japan, and Hatakeyama’s group collected influenza B isolates from 74 children before and after Tamiflu treatment and from 348 untreated patients suffering the flu.
Drug resistance noticed
The scientists discovered a type of the virus that had a decreased medication sensitivity in 1.4 per cent of the kids who had received Tamiflu. Additionally, they discovered that 1.7 per cent of the flu viruses from untreated patients had decreased sensitivity to Relenza, Tamiflu, or even both.
"Constant surveillance for the appearance or spread of neuraminidase inhibitor-resistant influenza viruses is extremely significant," the authors wrote. "Further assessment of the biological properties of neuraminidase inhibitor-resistant influenza viruses is necessary to evaluate entirely their pathogenicity in humans," they concluded.
Siegel also said: "The excessive use of Tamiflu based on fear of influenza may breed resistance. You want to save your medication for appropriate use, therefore you don’t breed resistance."
