Bird flu drug combo could extend supplies

Nov 2 2005

Doctors are saying that because of the scarcity of Tamiflu, presently being stockpiled by governments in the event of an influenza pandemic, supplies could be extended by giving it with another drug.

Advice to governments to stock up on Tamiflu, a prescribed drug for seasonal flu, because it will be a first line of defence against bird flu, have caused the spiraling demand for the drug.

It is of major concern that the present version of H5N1 bird flu circulating in Asia and reported in other areas, could mutate into a human pandemic strain.

According to Joe Howton, a medical director at the Adventist Medical Center in Portland, Oregon, probenecid, a treatment for gout which is used with some antibiotics to boost effectiveness, could have a similar impact with Tamiflu.

As yet no one knows how effective Tamiflu will be against a pandemic strain but it is considered the best option until a vaccine can be developed.

It appears that while Dr Howton was browsing through safety data published by the drug's Swiss manufacturer Roche, he noticed that giving Tamiflu with probenecid doubles the number of hours its active ingredient is in the blood.

Probenecid works by preventing the drugs from being removed from the body by the kidneys.

He says it dawned on him that the data potentially represented a tremendous therapeutic benefit.

If this is the case it would mean that half a dose of Tamiflu with probenecid would be as effective as a full dose without it.

But drug company Roche, who published the data on probenecid in 2002, said it could not advocate combined treatment because of the lack of clinical data and regulatory approval.

David Reddy, Roche's influenza pandemic task force leader, says in view of the present situation and the potential for a pandemic, they aim to dramatically increase the availability of the drug and make all information available.

To date more than 60 people have died from the H5N1 strain in Asia.

President George W. Bush has asked the U.S. Congress for $7.1 billion to prepare for a pandemic flu, including $1.2 billion for 20 million doses of a vaccine against H5N1 bird flu.

Roche has cranked up production of the drug but even the most optimistic estimates suggests the company can only meet a small fraction of global demand for the drug.

The company stopped deliveries of Tamiflu to the United States and Canada last week until the start of the flu season because the firm feared demand by companies and individuals could deplete stocks.