Acute and Longer-Term Outcomes Using Ketamine as a Clinical Treatment at the Yale Psychiatric Hospital

Objective: Ketamine has emerged as a rapid-acting antidepressant, though controversy remains whether sufficient data exist to justify its use outside of research protocols. In October 2014, the authors' institution began providing ketamine as an off-label therapy on a case-by-case basis for patients unable to participate in research protocols. Here, the participant experience during 29 months of providing ketamine as a clinical treatment for severe and treatment-resistant mood disorders through February 2017 is described. Methods: Patients were initially treated with a single-or double-infusion protocol (0.5 mg/kg for 40 minutes intravenously) and were later transitioned to a 4-infusion protocol over 2 weeks. Results: Fifty-four patients received ketamine, with 518 total infusions performed. A subset of 44 patients with mood disorders initiated the 4-infusion protocol, of whom 45.5% responded and 27.3% remitted by the fourth infusion. A subsample (n = 14) received ketamine on a long-term basis, ranging from 12 to 45 total treatments, over a course of 14 to 126 weeks. No evidence was found of cognitive decline, increased proclivity to delusions, or emergence of symptoms consistent with cystitis in this subsample. Conclusions: In general, ketamine infusions were tolerated well. The response and remission rates in this clinical sample were lower than those observed in some research protocols. The small number of patients who were treated on a maintenance schedule limits the conclusions that can be drawn regarding the long-term safety of ketamine; however, no long-term adverse effects were observed in this sample.