SELECTIVE SEROTONIN REUPTAKE INHIBITOR - A new class of antidepressant medicine that is slowly replacing tricyclic antidepressants as the drugs of choice for the treatment of depression in the United States. This is in part due to their much lower cardiac side effect profile. Examples of trade name products include Prozac, Paxil, Zoloft, Luvox, and Celexa. These agents work by selectively inhibiting the reuptake of the neurotransmitter 5-hydroxytryptophan (serotonin) by the nerve cells. This leads to the accumulation of serotonin in the brain and increased serotonin stimulation. Increasing serotonin activity in the patient who is depressed appears to improve the condition in many patients.