Objective: Suicidal ideation is a medical emergency, especially when severe. Little research has been done on pharmacologic interventions that could address this problem. Ketamine, an N-methyl-D-aspartate antagonist, has been reported to have antidepressant effects within hours. We examined the effects of a single dose of ketamine on suicidal ideation in subjects with treatment-resistant major depressive disorder (MDD). Method: Thirty-three subjects with DSM-IV-diagnosed MDD received a single open-label infusion of ketamine (0.5 mg/kg) and were rated at baseline and at 40, 80, 120, and 230 minutes postinfusion with the Scale for Suicide Ideation (SST), the Montgomery-Asberg Depression Rating Scale, the Hamilton Depression Rating Scale, and the Beck Depression Inventory. The study was conducted between October 2006 and January 2009. Results: Suicidal ideation scores decreased significantly on the SSI as well as on the suicide subscales of other rating instruments within 40 minutes; these decreases remained significant through the first 4 hours postinfusion (P<.001). Ten subjects (30%) had an SSI score 4 at baseline; all these scores dropped below 4 (9 dropped by 40 minutes and 1 by 80 minutes). For those patients with a starting score below 4 on the SSI, only 1 reached a score of 4. Depression, anxiety, and hopelessness were significantly improved at all time points (P<.001). Conclusions: Suicidal ideation in the context of MDD improved within 40 minutes of a ketamine infusion and remained improved for up to 4 hours postinfusion. Future studies with ketamine in suicidal ideation are warranted due to the potential impact on public health.
