Clinical Outcomes of Intravenous Ketamine Treatment for Depression in the VA Health System.

Objective/Background: Intravenous (IV) ketamine is effective for reducing symptoms of major depressive disorder in short-term clinical trials; this study characterized clinical outcomes of repeated infusions in routine clinical practice and the frequency and number of infusions used to sustain symptom improvement. Methods: Records of IV ketamine infusions for depression and associated Patient Health Questionnaire-9 (PHQ-9) scores were identified from Veterans Health Administration (VA) electronic medical records for patients treated in Fiscal Year 2020 and up to 12 months following the date of their first infusion. Results: Sample patients (n = 215) had a mean baseline PHQ-9 score of 18.6 and a mean of 2.1 antidepressant medication trials in the past year and 6.1 antidepressant trials in the 20 years prior to their first ketamine infusion. Frequency of infusions decreased from every 5 days to every 3-4 weeks over the first 5 months of infusions, with a mean of 18 total infusions over 12 months. After 6 weeks of treatment, 26% had a 50% improvement in PHQ-9 score (response) and 15% had PHQ-9 score ≤ 5 (remission). These improvements were similar at 12 and 26 weeks. No demographic characteristics or comorbid diagnoses were associated with 6-week PHQ-9 scores. Conclusions: While only a minority of patients treated with IV ketamine for depression experienced response or remission, symptom improvements achieved within the first 6 weeks were sustained over at least 6 months with decreasing infusion frequency. Further study is needed to determine optimal infusion frequency and potential for adverse effects with repeated ketamine infusions for depression.