Oral Administration of the NMDA Receptor Antagonist S-Ketamine as Add-On Therapy of Depression: A Case Series

We intended to assess safety, response to treatment and time to response of 1.25 mg/kg oral S-ketamine as add-on to standard antidepressants in four depressed patients. Two patients with melancholic depression responded early and stayed in remission, while two patients with distinct somatic symptoms, chronicity or atypical features did not respond. The limited number of patients does not allow conclusions about efficacy. Oral S-ketamine was well tolerated and could merit being studied in randomised controlled trials due to its higher practicability compared to (S-)ketamine infusion therapy. Clinical subtyping should be considered.