Oseltamivir, sold under the brand name Tamiflu, is an antiviral medication used to treat and prevent influenza A and influenza B, viruses that cause the flu. Many medical organizations recommend it in people who have complications or are at high risk of complications within 48 hours of first symptoms of infection. They recommend it to prevent infection in those at high risk, but not the general population. The Centers for Disease Control and Prevention (CDC) recommends that clinicians use their discretion to treat those at lower risk who present within 48 hours of first symptoms of infection. It is taken by mouth, either as a pill or liquid. Recommendations regarding oseltamivir are controversial as are criticisms of the recommendations. A 2014 Cochrane Review concluded that oseltamivir does not reduce hospitalizations, and that there is no evidence of reduction in complications of influenza. 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. Common side effects include vomiting, diarrhea, headache, and trouble sleeping. Other side effects may include psychiatric symptoms and seizures. In the United States it is recommended for influenza infection during pregnancy. It has been taken by a small number of pregnant women without signs of problems. Dose adjustment may be needed in those with kidney problems. Oseltamivir was approved for medical use in the US in 1999. It was the first neuraminidase inhibitor available by mouth. It is on the World Health Organization's List of Essential Medicines but was downgraded to "complementary" status in 2017. A generic version was approved in the US in 2016. In 2020, it was the 178th most commonly prescribed medication in the United States, with more than 3million prescriptions. Medical use Oseltamivir is used for the prevention and treatment of influenza caused by influenza A and B viruses. It is on the World Health Organization's List of Essential Medicines. The WHO supports its use for severe illness due to confirmed or suspected influenza virus infection in critically ill people who have been hospitalized. Oseltamivir's risk-benefit ratio is controversial. In 2017, it was moved from the core to the complementary list based on its lower cost-effectiveness. The Expert Committee did