The efficacy of ketamine in reducing suicidal ideation (SI) has been previously reported. We aimed to evaluate acute anti-SI effects of single-dose ketamine in different formulations/routes of administration by pooling results from randomized controlled trials (RCTs). A systematic search was conducted on Cochrane, Embase, Medline, and PubMed from inception to July 1st, 2020. Studies were selected based on pre-determined eligibility criteria. Effect sizes of different formulations/routes at various time points were computed using random-effects models. With data from nine eligible RCTs (n = 197), the pooled effect size for anti-SI effects at the 24-h time point was 1.035 (N = 6, CI: 0.793 to 1.277, p < 0.001) for intravenous (IV) racemic ketamine and 1.309 (N = 1, CI: 0.857 to 1.761, p < 0.001) for intranasal (IN) esketamine. An additional five RCTs were available for qualitative analysis. RCTs were identified for oral/sublingual ketamine for depression, however, none of these trials reported anti-SI effects preventing quantitative analysis for these routes of delivery. No RCTs for intramuscular (IM) ketamine were identified. The findings suggest that single-dose IV ketamine/IN esketamine is associated with robust reductions in suicidal thoughts at 2-h, 4-h, and 24-h post-intervention. In addition, future studies on IM/oral/sublingual ketamine and comparative studies are warranted to evaluate the anti-SI efficacy of distinct formulations and routes of administration.
Keywords: Glutamate; Mood disorders; NMDA; Suicidal ideation (SI).
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