Metabolic Syndrome Rather Than Body Mass Index Is Associated With Treatment Response to Ketamine Infusions.

Purpose: There is a practical need for the identification of pretreatment clinical and epidemiological response predictors to repeat ketamine infusions. Response predictors can serve to guide clinical inclusion of patients and weigh risks versus benefits for those receiving maintenance ketamine. Previous studies indicate a link between obesity, depression, and treatment response. We sought to investigate if body mass index (BMI) or metabolic syndrome could predict treatment response to ketamine.

Methods: Patients aged 18 to 72 years who were electroconvulsive therapy nonresponders were given a subanesthetic ketamine hydrochloride dose of 0.5 mg/kg delivered intravenously for 40 minutes for an acute series of 3 to 6 infusions every other day. If patients reported at least a 50% decrease in depression symptoms after the acute series, they were moved to a maintenance series of infusions, on an individualized basis. To assess if BMI or metabolic syndrome could predict response, logistic regression models were run to analyze initial responders, sustained responders, and nonresponders. Models were adjusted for age, sex, and baseline depression severity.

Results: Of the 150 patients analyzed, 56 did not respond to the acute phase, 38 initially responded to the acute phase but relapsed during the maintenance phase, and 56 sustained their response for 1 year. In unadjusted models, BMI was not shown to be a predictor of initial or sustained response. Alternatively, metabolic syndrome defined by a diagnosis of hypertension, hyperglycemia, or hyperlipidemia was determined to be significantly associated with diminished initial response but not sustained response.

Conclusions: In our patient group, results support the literature that outcome in antidepressant therapy is affected by the presence of metabolic syndrome rather than obesity itself. Although BMI did not predict initial response to ketamine, the presence of metabolic syndrome was significantly negatively associated with the initial response to an acute series of ketamine infusions.