Low‐dose ketamine infusion in treatment‐resistant double depression: Revisiting the adjunctive ketamine study of Taiwanese patients with treatment‐resistant depression

Background Whether a single low‐dose ketamine infusion may have rapid antidepressant and antisuicidal effects in patients with treatment‐resistant double depression remains unclear. Methods This study enrolled 35 patients with treatment‐resistant double depression, 12 of whom received 0.5 mg/kg ketamine, 11 received 0.2 mg/kg ketamine, and 12 received normal saline as a placebo. The patients were assessed using the 17‐item Hamilton Rating Scale for Depression (HDRS) prior to the initiation of infusions, at 40 and 240 min post‐infusion, and sequentially on Days 2–7 and on Day 14 after ketamine or placebo infusions. Results A single 0.5 mg/kg ketamine infusion had rapid antidepressant (p = 0.031, measured by the HDRS) and antisuicidal (p = 0.033, measured by the HDRS item 3 scores) effects in patients with treatment‐resistant double depression. However, 0.2 mg/kg ketamine was insufficient to exert rapid antidepressant and antisuicidal effects in this patient population with severe and chronic illness. Discussion In this patient population, the commonly used dose of 0.5 mg/kg was sufficient. Additional studies are required to investigate whether repeated infusions of low‐dose ketamine may also maintain antidepressant and antisuicidal effects in patients with treatment‐resistant double depression.