The infection that causes influenza is treated by a medication known as Tamiflu which is an antiviral neuraminidase inhibitor successful in treatment and prevention of both Influenza virus A and Influenza virus B. It acts as a transition-state analogue inhibitor of influenza neuraminidase, preventing new viruses from emerging from infected cells. Tamiflu is the only neuraminidase inhibitor that has been proven to fight the Bird Flu.

Being the first orally active neuraminidase inhibitor commercially developed, Tamiflu is a considered prodrug which is hydrolysed hepatically to the active metabolite, the free carboxylate of oseltamivir (GS4071). It was developed by Gilead Sciences and is marketed by Hoffmann-La Roche.

Because of increasing fears about a new influenza pandemic around the world, Tamiflu has received substantial media attention. Production capacity is limited, and governments are stockpiling the drug which has proved to be effective. The drug cannot be given out freely and has to be prescribed by a doctor.

Tamiflu was developed for the treatment of the influenza A and B virus in people at least one year of age, and prevention of influenza in people at least 1 year or older. Children under one year old should not be given the drug and there are reports are that it may have an adverse effect on infants under that age.

Treatment of influenza using Tamiflu for adults is 75 mg twice daily for 5 days, beginning within 2 days of the appearance of symptoms and with decreased doses for children and for patients with kidney problems. Tamiflu may be given as a preventive measure either during an outbreak in the community, or following close contact with an infected individual. The standard prophylactic dose is 75 mg once daily for patients aged 13 and older; this has been shown to be safe and effective for a period of up to six weeks.

H5N1-type influenza virus A infection avian influenza, commonly known as bird flu, should be treated with higher doses and longer durations. It has been found that the standard recommended dose suppresses viral replication in at least some patients with H5N1 influenza, rendering therapy non effective and therefore increasing the risk of viral resistance.

By administering Tamiflu with Probenecid it could extend the limited supply of the Tamiflu medication. Probenecid reduces renal excretion of the active metabolite of Tamiflu. A study has shown that 500 mg of Probenecid given every six hours doubled both the peak plasma concentration and the half-life of Tamiflu increasing overall systemic exposure.