Oseltamivir INN /ɒsəlˈtæmɨvɪər/, marketed under the trade name Tamiflu, is an antiviral medication used to treat influenza A and influenza B (flu), and to prevent flu after exposure. The medication is taken orally.The Infectious Disease Society of America, the United States' Centers for Disease Control and Prevention (CDC), and the United Kingdom's National Institute for Health and Care Excellence recommend the use of oseltamavir for people who have complications or are at high risk for complications who present within 48 hours of first symptoms of infection. They recommend its use to prevent infection in at-risk people but not the general population. The CDC recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. However, these recommendations are controversial as are criticisms of the recommendations. A Cochrane review concluded that oseltamivir does not reduce hospitalizations, and that there is no evidence of reduction in complications of influenza (such as pneumonia) because of a lack of diagnostic definitions, or reduction of the spread of the virus. Two meta-analyses have concluded that benefits in those who are otherwise healthy do not outweigh its risks. They also found little evidence regarding whether treatment changes the risk of hospitalization or death in high risk populations. However, another meta-analysis found that oseltamivir was effective for prevention of influenza at the individual and household levels.Side effects include psychiatric symptoms, increased rates of vomiting, and headaches. It is pregnancy category C in the United States and category B in Australia meaning that it has been taken by a small number of women without signs of problems and in animal studies it looks safe. Dose adjustment may be needed in those with kidney problems.It was the first orally administered neuraminidase inhibitor commercially developed. It was discovered and developed by US-based Gilead Sciences, which licensed the exclusive rights to Roche in 1996. It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.