The generic drugs amantadine and rimantadine could be effective against the avian flu, according to a study to be published in the next issue of the Journal of Infectious Diseases.

Most strains of the lethal avian influenza virus H5N1 -- which has killed more than half of the 207 people it has infected -- could be treated with these older antivirals, the study says.

"Amantadine appears to retain the potential to be useful in an H5N1 pandemic in the absence of a vaccine, as a prophylactic agent and as a component of combination antiviral therapy," study authors say.

Both drugs are available in generic formulations from multiple sources, including Sandoz for amantadine and Impax for rimantadine, according to the FDA.

Researchers analyzed 638 H5N1 viruses of human and avian origin from Hong Kong and eight Asian nations. More than 90 percent of the virus strains from Vietnam and Cambodia had mutations that made them resistant to amantadine and rimantadine, but only 6.3 percent of the strains from Indonesia and 8.9 percent from China had these mutations.

The study can be found at http://www.journals.uchicago.edu/ucp/WebIntegrationServlet?call=ContentWeblet&url=http://www.journals.uchicago.edu/JID/journal/issues/v193n12/36344/36344.web.pdf¤t_page=content (http://www.journals.uchicago.edu/ucp/WebIntegrationServlet?call=ContentWeblet&url=http://www.journals.uchicago.edu/JID/journal/issues/v193n12/36344/36344.web.pdf¤t_page=content).