Clinical Effectiveness of Intravenous Racemic Ketamine Infusions in a Large Community Sample of Patients With Treatment-Resistant Depression, Suicidal Ideation, and Generalized Anxiety Symptoms: A Retrospective Chart Review

ABSTRACT

Introduction: Few studies have been published to date exploring the effectiveness of ketamine for treatment-resistant depression (TRD) in large clinical samples. We report on the clinical outcomes of a large cohort treated with ketamine as part of clinical practice.

Methods: Deidentified electronic chart data were obtained from a multisite private ketamine infusion clinic for 424 patients with TRD seen from November 9, 2017, to May 4, 2021. Ketamine infusions were administered at a starting dose of 0.5 mg/kg/40 minutes for 6 infusions within 21 days. Maintenance infusions were offered based on clinical response. Changes in outcome measures (scores on the Patient Health Questionnaire-9 [PHQ-9] and Generalized Anxiety Disorder-7 [GAD-7]) within subjects were analyzed using longitudinal multilevel modeling with Kaplan-Meier estimates. Logistic regression was used to analyze for a priori theorized potential moderators of response.

Results: Significant improvements from baseline were observed over time on the main outcomes (all P < .001). Based on PHQ-9 self-report data, within 6 weeks of infusion initiation, a 50% response rate and 20% remission rate for depressive symptoms were observed. Response and remission rates were 72% and 38%, respectively, after 10 infusions, and there was a 50% reduction in self-harm/suicidal ideation (SI) symptom scores within 6 weeks. Half of patients with SI at baseline no longer had it after 6 infusions. A 30% reduction in anxiety symptoms (per the GAD-7) was observed.

Conclusions: Ketamine was effective at reducing symptoms of SI, depression, and anxiety. The high rates of response and remission were similar to those for interventional treatments in community samples of TRD. Comparative efficacy trials with other interventions and randomized controlled trials of racemic ketamine infusion as the primary treatment for SI are needed.