April 30 (Bloomberg) -- Health officials battling a flu pandemic should consider first using stockpiles of a drug in shorter supply, such as GlaxoSmithKline Plc’s Relenza, before switching to Roche Holding AG’s Tamiflu, a study said.

Researchers at Harvard University and the University of Hong Kong said that strategy, if used early in an outbreak, may delay the development of resistance to the more plentiful antiflu drug. They used a mathematical model and predicted that treating as few as 1 percent of people in areas of an epidemic with the less common Relenza might substantially delay resistance to Tamiflu, the drug in wider use.

If the swine flu continues to spread, it will probably lead to “unprecedented levels of use” of Tamiflu, the antiviral drug most developed countries have stockpiled, said Marc Lipsitch, an epidemiologist at the Harvard School of Public Health in Boston. That is likely to lead to the emergence of a new strain of the H1N1 flu virus that is resistant to Tamiflu, he said in a conference call today with reporters.

“Ideally we’d like to delay the appearance of those resistant strains as long as we can,” he said during the call. “If a country has a second drug and could use it for as little as 1 percent to 1.5 percent of cases, it could make a major difference.”

The scientists’ analysis was published today in PLoS Medicine, an online journal of the Public Library of Science, based in San Francisco. The mathematical model was prepared before the recent emergence of swine flu. Lipsitch said he had been working almost around the clock for the last few days applying the model to the current outbreak.

The researchers also considered an alternate strategy for delaying development of drug resistance -- treating patients from the start with a combination of two drugs.

That strategy, while equally effective in theory at delaying resistance to the primary drug, can’t be applied in this case because no studies have shown that combining Relenza with Tamiflu is safe, Lipsitch said.

To contact the reporter on this story: Rob Waters in San Francisco at rwaters5@bloomberg.net.

Last Updated: April 30, 2009 16:21 EDT