Serotonin reuptake inhibitors: the corner stone in treatment of depression for half a century--a medicinal chemistry survey.

Inhibition of serotonin (5-HT) reuptake has been a central theme in the therapy of depression for half a century. Through the years these therapies have improved, particularly with regard to side effects, and today's selective serotonin reuptake inhibitors (SSRIs) constitute a reasonably effective offer for the patients. However, there is still room for major improvement and considering that almost 20% of the population in the western world will experience a depressive period in their lifetime, there is a large need for improved therapies. A large spectrum of targets and strategies are currently being pursued, but so far none of these new approaches have been successful, mainly due to lack of a deeper understanding of the disease biology. Since inhibition of 5-HT reuptake ensures a certain degree of antidepressant efficacy, there has been a large interest in various combinations with serotonin reuptake inhibitors (SRIs) in order to improve on the shortcomings of treatment with SSRIs. Some of these approaches have resulted in marketed antidepressants, eg combinations of SRI with norepinephrine (NE) reuptake inhibition, whereas other approaches are still at an experimental stage. This review attempts to present the current status of these add-on/combination approaches with particular focus on the medicinal chemistry aspects.