Fluoxetine, sold under the brand names Prozac and Sarafem, among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used for the treatment of major depressive disorder, obsessive–compulsive disorder (OCD), bulimia nervosa, panic disorder, and premenstrual dysphoric disorder. It is also approved for treatment of major depressive disorder in adolescents and children 8 years of age and over. It has also been used to treat premature ejaculation. Fluoxetine is taken by mouth.Common side effects include indigestion, trouble sleeping, sexual dysfunction, loss of appetite, dry mouth, and rash. Serious side effects include serotonin syndrome, mania, seizures, an increased risk of suicidal behavior in people under 25 years old, and an increased risk of bleeding. Antidepressant discontinuation syndrome is less likely to occur with fluoxetine than with other antidepressants, but it still happens in many cases. Fluoxetine taken during pregnancy is associated with significant increase in congenital heart defects in the newborns. It has been suggested that fluoxetine therapy may be continued during breastfeeding if it was used during pregnancy or if other antidepressants were ineffective.Fluoxetine was discovered by Eli Lilly and Company in 1972, and entered medical use in 1986. It is on the World Health Organizations List of Essential Medicines. It is available as a generic medication. In 2020, it was the 25th most commonly prescribed medication in the United States, with more than 23 million prescriptions. Lilly also markets fluoxetine in a fixed-dose combination with olanzapine as olanzapine/fluoxetine (Symbyax).
The invention of using fluoxetine to treat PMDD was made by Richard Wurtman at MIT; the patent was licensed to his startup, Interneuron, which in turn sold it to Lilly.To defend its Prozac revenue from generic competition, Lilly also fought a five-year, multimillion-dollar battle in court with the generic company Barr Pharmaceuticals to protect its patents on fluoxetine, and lost the cases for its line-extension patents, other than those for Sarafem, opening fluoxetine to generic manufacturers starting in 2001. When Lillys patent expired in August 2001, generic drug competition decreased Lillys sales of fluoxetine by 70% within two months.In 2000 an investment bank had projected that annual sales of Sarafem could reach $250M/year. Sales of Sarafem reached about $85M/year in 2002, and in that year Lilly sold its assets connected with the drug for $295M to Galen Holdings, a small Irish pharmaceutical company specializing in dermatology and womens health that had a sales force tasked to gynecologists offices; analysts found the deal sensible since the annual sales of Sarafem made a material financial difference to Galen, but not to Lilly.Bringing Sarafem to market harmed Lillys reputation in some quarters. The diagnostic category of PMDD was controversial since it was first proposed in 1987, and Lillys role in retaining it in the appendix of the DSM-IV-TR, the discussions for which got under way in 1998, has been criticized. Lilly was criticized for inventing a disease in order to make money, and for not innovating but rather just seeking ways to continue making money from existing drugs.