A preliminary study of adjunctive ketamine for treatment-resistant bipolar depression

Objectives: Ketamine has shown rapid antidepressant effects in depressed patients. However, the antidepressant and antisuicidal effects of repeated ketamine infusions in patients with treatment-resistant bipolar depression (TRBD) are not known. Methods: TRBD patients received six intravenous infusions of 0.5 mg/kg ketamine over 40 min on a Monday Wednesday Friday schedule during a 12-day period followed by a 2-week follow-up period. Depressive symptoms were measured by the Montgomery-Asberg Depression Rating Scale (MADRS) at baseline and at each follow-up visit. Results: Nineteen patients with TRBD were enrolled in the study, and 16 patients (84.2%) received all six ketamine infusions. After the first infusion, the rates of response and remission were 21.1% (95% CI: 0.9 to 21.2) and 15.8% (95% CI: 0 to 33.9), respectively, and after the sixth infusion, the rates of response and remission were 73.7% (95% CI: 51.9 to 95.5) and 63.2% (95% CI: 39.3 to 87.0), respectively. The average times for nineteen patients who responded and remitted were 9.1 and 12.5 days, respectively. There were large decreases in the scores on the MADRS and the Scale for Suicidal Ideation-part 1 within 4 h after the first infusion, and the decreases were maintained across subsequent infusions. There were no significant increases in dissociative and psychotomimetic symptoms as measured by the Clinician-Administered Dissociative States Scale (CADSS) and the Brief Psychiatric Rating Scale (BPRS)-4 items, respectively. Conclusion: These pilot findings suggest the feasibility of repeated ketamine infusions at subanaesthetic doses for patients with TRBD. Future controlled studies are needed to confirm and expand these findings.