A Preliminary Study of Intravenous Ketamine in Selective Serotonin Reuptake Inhibitor (SSRI)-Resistant Depression

This single-site, non-randomised Phase II trial enrolled 20 patients with SSRI‑resistant major depression to receive intravenous ketamine once weekly for three weeks.

The primary outcome was change in depressive symptoms assessed two weeks after the final infusion; secondary objectives included measurement of biomarkers (cytokines, tryptophan metabolism and endocrine parameters) pre- and post-treatment and at longer-term follow-up.

Sponsor was the Department of Psychiatry, University College Cork; IMP was ketamine hydrochloride (Ketalar), provided by Pfizer Healthcare Ireland.