Rapid and Sustained Reductions in Current Suicidal Ideation Following Repeated Doses of Intravenous Ketamine: Secondary Analysis of an Open-Label Study

Background: Ketamine rapidly reduces thoughts of suicide in patients with treatment-resistant depression who are at low risk for suicide. However, the extent to which ketamine reduces thoughts of suicide in depressed patients with current suicidal ideation remains unknown.

Methods: Between April 2012 and October 2013, 14 outpatients with DSM-IV-diagnosed major depressive disorder were recruited for the presence of current, stable (≥ 3 months) suicidal thoughts. They received open-label ketamine infusions over 3 weeks (0.5 mg/kg over 45 minutes for the first 3 infusions; 0.75 mg/kg over 45 minutes for the last 3). In this secondary analysis, the primary outcome measures of suicidal ideation (Columbia-Suicide Severity Rating Scale [C-SSRS] and the Suicide Item of the 28-item Hamilton Depression Rating Scale [HDRS28-SI]) were assessed at 240 minutes postinfusion and for 3 months thereafter in a naturalistic follow-up.

Results: Over the course of the infusions (acute treatment phase), 7 of 14 patients (50%) showed remission of suicidal ideation on the C-SSRS Ideation scale (even among patients whose depression did not remit). There was a significant linear decrease in this score over time (P < .001), which approached significance even after controlling for severity of 6-item Hamilton Depression Rating Scale (HDRS6) core depression items (P = .05). Similarly, there were significant decreases in the C-SSRS Intensity (P < .01) and HDRS28-SI (P < .001) scores during the acute treatment phase. Two of the 7 patients who achieved remission during the acute treatment phase (29%) maintained their remission throughout a 3-month naturalistic follow-up.

Conclusions: In this preliminary study, repeated doses of open-label ketamine rapidly and robustly decreased suicidal ideation in pharmacologically treated outpatients with treatment-resistant depression with stable suicidal thoughts; this decrease was maintained for at least 3 months following the final ketamine infusion in 2 patients.

Trial Registration: ClinicalTrials.gov identifier: NCT01582945