Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) antidepressant. Fluoxetine affects chemicals in the brain that may be unbalanced in people with depression, panic, anxiety, or obsessive-compulsive symptoms. Fluoxetine is used to treat major depressive disorder, bulimia nervosa (an eating disorder), obsessive-compulsive disorder, panic disorder, and premenstrual dysphoric disorder (PMDD).