The effectiveness, tolerability, and safety of intravenous (IV) ketamine in adults with treatment resistant depression (TRD) receiving care in real-word settings is insufficiently characterized. Herein, results from a naturalistic, retrospective study are presented from a Canadian outpatient IV ketamine clinic.

Adults (N = 213; M_age = 45) with Major Depressive Disorder or Bipolar Disorder, with a minimum of Stage 2 antidepressant resistance, received IV ketamine at a community-based multi-disciplinary clinic. The primary outcome measure was change from baseline to post-infusion 4 on the Quick Inventory for Depression Symptomatology-Self Report-16 (QIDS-SR₁₆; n = 190). Secondary measures included QIDS-SR₁₆-measured response and remission rates, changes from baseline to endpoint in Generalized Anxiety Disorder-7 Scale (GAD-7; n = 188) and the Sheehan Disability Scale (SDS; n = 168).

Significant improvement in total depressive symptoms severity (p < 0.0001) was observed after four infusions of IV ketamine 0.5–0.75 mg/kg. Moreover, the response rate (QIDS-SR₁₆ total score change ≥ 50%) was 27% and remission (QIDS-SR₁₆ total score ≤5) rate was 13%. Patients receiving IV ketamine exhibited anxiolytic effects (p < 0.0001,), improved overall psychosocial function (p < 0.0001), and reduced suicidal ideation (p < 0.0001). Compared to the baseline infusion, dissociation severity significantly reduced in subsequent infusions.

This was a naturalistic, retrospective study, without a control group.

IV ketamine was safe, well-tolerated, and effective at improving depressive, anxiety, and functional impairment symptoms in a well-characterized cohort of adults with TRD.