selective serotonin reuptake inhibitor (SSRI), an antidepressant drug that blocks reuptake of serotonin without blocking reuptake of other biogenic amines such as norepinephrine and dopamine. Advantages over tricyclic antidepressant drugs include fewer anticholinergic side effects (dry mouth, blurred vision, urinary retention) and fewer antihistaminic side effects (sedation, weight gain).