Use of repeated intravenous ketamine therapy in treatment-resistant bipolar depression with suicidal behaviour: a case report from Spain

Introduction

Ketamine is a non-competitive NMDA receptor antagonist and a dissociative anaesthetic that has long been used in anaesthesiology, particularly in paediatrics. Its use in adults has been controversial because of dissociative and psychotomimetic adverse effects and potential for misuse. Since the first report of antidepressant effects about 15 years prior to this paper, systematic reviews and meta-analyses have described rapid and robust antidepressant and anti‑suicidal effects of ketamine, while also noting that these benefits are typically transient and that double‑blind trials face methodological challenges. This case report presents an additional clinical observation intended to inform how ketamine might be used in treatment‑refractory depression (TRD). Specifically, the authors describe the use of repeated intravenous ketamine infusions in a patient with refractory bipolar depression and chronic suicidal behaviour, documenting the treatment rationale, clinical course, tolerability and the durability of response. The report aims to contribute to the limited Spanish literature on off‑label ketamine use in severe mood disorders and to highlight the unresolved issue of how best to sustain benefit after initial response.