Seroxat antidepressant pills. These contain the SSRI (selective serotonin reuptake inhibitor) drug paroxetine that is only available on prescription. Paroxetine is used to treat depressive illnesses, obsessive-compulsive disorder, panic disorder and agoraphobia. By inhibiting serotonin reuptake, it prolongs its effects on the brain. Serotonin is a brain chemical that helps regulate moods. Seroxat is produced by GlaxoSmithKline Pharmaceuticals.