Long-term outcomes of repeated ketamine infusions in patients with unipolar and bipolar depression: A naturalistic follow-up study

Objective: Ketamine was proven to have short-term antidepressant effects. There is a paucity of studies focused on the long-term outcomes of repeated infusions of ketamine. This study aimed to examine the long-term outcomes of repeated ketamine infusions in patients with unipolar and bipolar depression Methods: One hundred and eight patients with unipolar and bipolar depression completed the repeated treatment phase (administered ketamine three times weekly over a 12-day) and entered a 9-month naturalistic follow-up phase. Assessments were obtained at week 2, month 6, and month 9 after the repeated treatment phase. The Patient Health Questionnaire-9 (PHQ-9) Scale and the Global Assessment of Functioning (GAF) Scale were used to assess depressive symptoms and global functional status, respectively. Results: Seventy-one (65.7%) of patients completed the 9-month follow-up. On month 9, the response and remission rate were 80.3% and 78.9%, respectively. Among 56 patients who achieved response after the repeated treatment phase, 26 (46.4%) of patients sustained response during 9-month follow-up and their GAF score remained over 70. Sixteen patients relapsed during the 9-month follow-up and 14 (85.7%) of the relapse occurred during the first 2-week follow-up. Limitation: The major limitation of this study is the open-label design. Conclusions: This small sample study suggested that patients with unipolar and bipolar depression who response to repeated treatment with continued oral antidepressant may be a viable treatment option, and their global functional status improved with a follow-up. Relapse of depression tended to occur during the 2 weeks follow-up.