What Exactly Is Paxil?   Paroxetine, which is sold under the brand names Paxil and Seroxat, is a selective serotonin reuptake inhibitor (SSRI) antidepressant. It is prescribed for the treatment of major depressive disorder, obsessive-compulsive disorder, panic disorder, social anxiety disorder, posttraumatic stress disorder, generalized anxiety disorder, and premenstrual dysphoric...