A drug that reduces Tamiflu (oseltamivir phosphate) excretion by the kidneys could effectively double the number of doses of Tamiflu available in an influenza pandemic.

Last week, Joe Howton, medical director at the Adventist Medical Center in Portland, Oregon, suggested a way to double supplies, after browsing basic safety data from Roche for a talk on avian flu.

The technique was invented during the Second World War to extend precious penicillin supplies. Scientists found that a simple benzoic acid derivative called probenecid stops many drugs, including antibiotics, being removed from the blood by the kidneys. Probenecid is readily available and is still widely used alongside antibiotics to treat gonorrhoea and syphilis, and in emergency rooms, where doctors need their patients to have high, sustained levels of antibiotics in their blood.

Howton believes that Tamiflu doses could be cut in half when taken with Probenecid. This would effectively double the amount of Tamiflu available should a pandemic occur. To make this work Probenecid would need to be made in sufficient quantity. But quite possibly other existing drugs could be found that also interfere with Tamiflu excretion.

Sure enough, the Probenecid-Tamiflu excretion interaction is easy to find in descriptions of Tamiflu.

Drugs that may adversely interact with Tamiflu are the drugs containing Probenecid. Combining Tamiflu and drugs containing Probenecid may result in higher blood levels for patients.

Here is the two fold Tamiflu increase from Probenecid that Howton found:

Coadministration of probenecid results in an approximate 2-fold increase in exposure to the active metabolite due to a decrease in active anionic tubular secretion in the kidney. Other drugs excreted via anionic tubular secretion have not been evaluated.

If you haven't already stockpiled your own Tamiflu supply your odds of getting Tamiflu during a pandemic are rather slim even if Probenecid works to stretch Tamiflu supplies. The key to surviving a highly lethal influenza pandemic would be to greatly reduce your exposure to other people who might be influenza carriers. My favorite proposal for reducing the risk of getting a pandemic virus while simultaneously reducing the economic disruption of a pandemic is "workplace cocooning".

I also think we should have large crash programs for the development of cellular methods for growing flu vaccine and for the development of DNA vaccines as well. Plus, I'd gladly take a shot of a vaccine against existing H5N1 avian flu strains as a way to get partial immunity against an eventual possible human pandemic strain of H5N1.

Update: Do not casusally go taking probenecid to avoid the flu. First off, it does no good unless taken in combination with Tamiflu. Second, probenecid has potentially dangerous side effects and should not be taken casually. Do not take extra doses. You could kill yourself if you do.