Ketamine Plus Lithium in Treatment-Resistant Depression

The purpose of this study is to test the antidepressant effect of ketamine when given repeatedly over a period of 1 week, as well as the use of Lithium as a relapse-prevention strategy for patients with treatment-resistant depression (TRD) who respond to an initial series of ketamine infusions. Ketamine is a Food and Drug Administration approved anesthetic (a drug used to produce loss of consciousness before and during surgery). Ketamine is not approved for the treatment of major depressive disorder and is considered experimental in this study. An additional purpose of this study is to research the effects of ketamine on brain function. You may qualify to take part in this research study because you have been diagnosed with major depressive disorder (MDD) and have not responded to past treatments.