Major depression is a chronic, disabling disorder with an estimated lifetime prevalence of 16.6% in the U.S. Recent findings from a major research study indicate that up to 50% of patients do not recover after treatment with one selective serotonin reuptake inhibitor (SSRI). For patients who do not respond to SSRI treatment the next step is to switch to a non-SSRI drug or to try another SSRI. A study of 396 patients in the U.S. compared the effectiveness of the non-SSRI drug venlafaxine to the SSRI citalopram. The researchers found that overall both drugs had a similar level of effectiveness but that venlafaxine was more effective in severely depressed people. 57.8% of people taking venlafaxine suffered from side effects whereas 63.4% of people taking citalopram did. 24.5% of the people taking venlafaxine dropped out of the trial compared to 20.9% of those taking citalopram.
Lenox-Smith, Alan J. and Jiang, Qin - Venlafaxine extended release versus citalopram in patients with depression unresponsive to a selective serotonin reuptake inhibitor. International Clinical Psychopharmacology May 2008, 23(3), 113-119