Ketamine in the Treatment of Depression

• Ketamine Dose-Response Curve [ Time Frame: Baseline and Day 1 (post ketamine) ] [ Designated as safety issue: No ]
  The primary outcome is the dose-response curve as it refers to ketamine inducing a dose-dependent reduction in the 24-item Hamilton Depression Rating Scale (HDRS-24) scores of patients with major depressive disorder.
  
  

Major depressive disorder (MDD) is a common illness, affecting over 14 million American adults each year. MDD is a leading cause of disability worldwide, and is responsible for huge workplace and healthcare costs. The several week delay between onset of treatment and improvement in MDD symptoms with currently available treatments further increases the burden of the disorder. Shortening this delay is a major unmet challenge in the treatment of MDD. Studies report that a single intravenous low dose of a drug called ketamine can bring about substantial improvement in depression in hours, even in patients that have not improved with other antidepressant treatments. Certain aspects of ketamine's drug action are fairly well understood, but the question remains of how these properties relate to antidepressant effect. Our preliminary data support the rapid antidepressant benefit from ketamine. The investigators have used a scanner to measure the effects of ketamine on two major brain chemical transmitters and found that it causes a significant increase (more than 60%) in glutamate (Glu) and gamma aminobutyric acid (GABA) levels in the front of the brain. The investigators hypothesize that this increase in Glu and GABA levels, is responsible for the antidepressant action of the medication. Knowing how ketamine works could help to develop better medications that can be used orally and used for maintenance of the improvement seen with ketamine. The objective of the proposed dose finding study is to examine the relationship between the ketamine-induced improvement of MDD and the Glu and GABA responses to ketamine and to compare the Glu and GABA responses to ketamine in MDD and healthy subjects to better understand the pathophysiology of MDD. To achieve these aims this the investigators propose a randomized, placebo-controlled, double blind study with several different doses of ketamine. The investigators will conduct MRI scans to measure Glu and GABA before and during the ketamine treatment.