Antidepressants with selective serotonin reuptake inhibitors (SSRIs) aid with OCD by preventing serotonin absorption in the brain, which maintains levels in the body higher. Some OCD sufferers feel that medication helps them, while others find that it worsens their compulsive thinking. Research shows that fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil) may be more effective than placebo in reducing obsessive-compulsive symptoms. Tricyclic antidepressants (TCAs) work by blocking both serotonin and norepinephrine receptors, which can have additional benefits for those who suffer from anxiety as well as OCD symptoms. Examples of TCAs include amitriptyline (Nytrip), clomipramine (ClomiPril), and imipramine (Tofranil). Monoamine oxidase inhibitors (MAOIs) block an enzyme called monoamine oxidase, which is responsible for breaking down serotonin and other neurotransmitters in the brain. Because excessive amounts of serotonin are thought to play a role in causing OCD, this drug class is also used to treat related disorders such as panic disorder and depression. Examples of MAOIs include phenelzine (Nortriptyline), tranylcypromine (Parnate).