Selective-serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medications for depression.  The name “selective-serotonin reuptake inhibitor” indicates how the medicine works in the brain by altering serotonin, one of the brains naturally occurring chemical messengers.  SSRIs attach to cells in the brain in a way that interferes with the cell’s ability to vacuum back up the serotonin, which ends up causing more serotonin to remain in the spaces between brain cells.  Changing this balance in serotonin levels modifies how different parts of the brain communicate with each other and can in turn improve depression symptoms. This understanding of how SSRIs work, and their improvement of depressive symptoms has facilitated a common belief in the “chemical imbalance” theory of depression, or the idea that low serotonin causes depression. However, the relationship between serotonin and depression is likely more complex than that. As an analogy, ibuprofen is helpful for a headache but headaches are not believed to be caused by low levels of ibuprofen in the brain.

What are the different types of SSRIs and what are their characteristics?  The Federal Drug Administration has approved several types of SSRIs for treating depression.  Each is listed in the table below along with important characteristics such as names, doses, and side effects.


Brand Name

Generic Name

Usual Dosage Range (adults)

Side Effects



20-40 mg

Dizziness, headache, sleep disturbances, dry mouth, nausea



10-20 mg

Dizziness, sleep disturbances, dry mouth, nausea, weight changes, sexual dysfunction



20-80 mg

Restlessness, skin problems, pains


Paxil, Pexeva

20-50 mg

Dizziness, headache, sleep disturbances, dry mouth, nausea, sexual dysfunction, nervousness



50-200 mg

Headache, insomnia, agitation, nausea, diarrhea, sexual dysfunction

Special Considerations.

Fournier, JC., DeRubeis, RJ, Hollon, SD, Dimidjian, S., Amsterdam, JD, Shelton, RC and Fawcett, J. Antidepressant drug effects and depression severity: A patient-level meta-analysis. JAMA, 303(1), 47-53.


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