Generic Paroxetine: Paxil 20mg is used to treat depression, panic disorders, social anxiety disorders, obsessive compulsive disorders, generalized anxiety disorders, and post traumatic stress disorder. Paxil is in a class of medications called selected serotonin reuptake inhibitors. It works by increasing the amount of serotonin, a natural substance in the brain that helps maintain mental balance. Paxil 20mg TABLETS CAN be split in half.