While several open label studies have reported good response and remission rates when switching for non-response and poor tolerance reasons, several randomized controlled studies and meta-analyses have reported no difference in outcome when switching within a class of antidepressants versus switching to another class of antidepressant. For example, there were no differences in response to remission when non-remitters to citalopram were switched to another SSRI (sertraline) or to non-SSRI agents (bupropion-RS or venlafaxine-XR) (Rush et al., 2006).
Overall, there is no conclusive evidence to support switching to a different class over switching within the same class of antidepressants (Lam et al., 2009).