Want to treat your mental disorder, such as depression, panic attacks, or obsessive-compulsive disorder). Its also used to treat your eating disorder (bulimia) and a severe form of premenstrual syndrome. Fluoxetine belongs to a class of drugs known as selective serotonin reuptake inhibitors (SSRI). It works by helping to restore the balance of serotonin in the brain. Take this medicine by mouth as directed by your doctor, usually once daily in the morning. the dosage should be taken according to your medical conditions.