Oseltamivir (Tamiflu), approved in late 1999 to treat influenza, was recently approved by the FDA for the prevention of flu in adults and children 13 years or older. The drug acts by blocking the enzyme neuraminidase, which is required for viral replication.

In studies of the drug's prophylactic effects during a community outbreak, the incidence of laboratory-confirmed flu in healthy adults and adolescents who received oseltamivir for 42 days during flu season was 1.2%, compared with 4.8% in those who received a placebo. In a study of elderly nursing home residents, the incidence of laboratory-confirmed flu in those who took the drug for 42 days during flu season was 0.4%, compared with 4.4% in the placebo group.

In a separate study of post-exposure prophylaxis, household contacts of persons with flu symptoms that had begun within two days were randomly assigned to receive either oseltamivir or placebo once daily for seven days. The incidence of flu in the group taking oseltamivir was 1%, compared with 12% in the group that received placebo.

The regimen for postexposure prophylaxis is 75 mg once daily for seven days, started within two days of exposure. During a community outbreak, one 75-mg tablet may be taken daily for up to six weeks.

For prescribing information, go to http://www.rocheusa.com/products/tamiflu.

Food and Drug Administration. FDA approves Tamiflu for another indication-prevention of influenza. FDA Talk Paper. 2000 Nov 20.