What is Prozac? Prozac is the brand name of Fluoxetine. Prozac is a selective serotonin reuptake inhibitors (SSRI) antidepressant. Prozac affects chemicals in the brain that may become unbalanced and cause depression, panic, anxiety, or obsessive-compulsive symptoms. Prozac is used to treat major depressive disorder, bulimia nervosa (an eating disorder) obsessive-compulsive disorder, panic disorder, and premenstrual dysphoric disorder (PMDD).