Efficacy and Safety of Ketamine/Esketamine in Bipolar Depression in a Clinical Setting

Background: Bipolar disorder represents a significant source of morbidity and elevated mortality risk. Ketamine has emerged as a powerful antidepressant; however, there have been few trials of ketamine in bipolar depression and no trials with esketamine in bipolar depression, and few data exist from real-world settings. Here, we report outcomes from a cohort of patients with bipolar depression treated with ketamine/ esketamine in a real-world setting.

Methods: Patients with treatment refractory bipolar depression were referred to Yale Psychiatric Hospital Interventional Services for treatment from October 2014 to November 2023. Appropriate patients were treated with intravenous (IV) ketamine (0.5 mg/kg over 40 minutes) or intranasal esketamine (56 or 84 mg). Diagnosis of bipolar depression was done by clinical evaluation by an attending psychiatrist, based on DSM criteria. Clinical outcomes were tabulated from medical records.

Results: Overall, 45 patients with bipolar depression were treated with IV ketamine or intranasal (IN) esketamine during the time period specified. Depression severity outcomes were available for 38 patients that completed an acute series, defined as treatment twice weekly for up to 4 weeks. Overall, 15/38 (39%) achieved clinical response (≥50% improvement on the Montgomery-Asberg Depression Rating Scale [MADRS]) and 5/38 (13.2%) achieved remission (≤10 on MADRS) following the acute series. Mean MADRS scores decreased from 31.1 to 19.2 (38.3% mean improvement). Safety data (hypomania/manic symptoms) were available for all 45 patients (518 patient-months of follow-up). No patients experienced any mania/hypomania during the acute series phase (when treatments are given twice weekly). However, 13/45 (28.9%) patients experienced symptoms consistent with a hypomanic or manic episode at some point following the acute phase while continuing to receive ketamine or esketamine during a maintenance phase. There were 16 manic/hypomanic events, indicating 1 event for every 2.7 patient-years. Only 1 event was severe and resulted in hospitalization.

Conclusion: In a small sample of patients with bipolar depression treated with ketamine/esketamine, no evidence of mania/hypomania was seen during the acute phase of treatment. Further research is needed to evaluate whether ketamine or esketamine confers heightened risk of affective switch during maintenance treatment.