Thus, linezolid has the potential for causing serotonin syndrome (a hyperserotonergic state characterized by mental status changes, neurologic abnormalities, and autonomic instability) when it is used in patients with either of the following: Endocrinologically active carcinoid tumors Use of drugs with serotonergic activity Such drugs include selective serotonin reuptake inhibitors, MAOIs (eg, phenelzine, isocarboxazid), tricyclic antidepressants, serotonin 1B, 1D receptor agonists (triptans), meperidine, bupropion, and buspirone.