Evidence Summary
Single-dose IV ketamine elicits a short-term response
A meta-analysis of RCTs evaluating a single dose of IV ketamine vs placebo for severe depression found that it increased the chance of a treatment response for up to 1 week afterward. Studies included patients with severe (N = 30), treatment-resistant (N = 40), and psychotic depression (N = 10), based on Diagnostic and Statistical Manual of Mental Disorders–Fifth Edition criteria.1
The primary outcome was treatment response: either an improvement of > 50% on a standardized depression scale or a Clinical Global Impression–Improvement scale score of 1 or 2 (“very much” and “much” improved, respectively, as assessed by a clinician). Ketamine increased the likelihood of short-term response or improvement at 24 hours (3 RCTs; N = 56; odds ratio [OR] = 11; 95% CI, 2-58); at 72 hours (3 RCTs; N = 56; OR = 13; 95% CI, 2-66); and at 7 days (4 RCTs; N = 88; OR = 2.6; 95% CI, 1.1-6.2).1 Response rates equaled placebo at 2 weeks. The authors rated the RCTs as low quality.
Another systematic review of single-dose IV ketamine vs placebo for major depression and bipolar disorder included 3 additional small, low-quality RCTs, 2 of which showed short-term response to ketamine. The authors used Hedge’s g statistic to standardize effect size (a score of magnitude 0.2 indicates a small effect; 0.6, moderate; 1.2, large; and 2, very large). One RCT (n = 26) found a very large 1-day response (effect size: –2; 95% CI, –2.8 to –1.3), and 2 RCTs found conflicting responses at 12 days (RCT with N = 18: effect size: –0.2; 95% CI, –0.4 to 0.02 [no significant response] vs RCT with N = 8: effect size: –1.5; 95% CI, –2.5 to –0.5).2
More frequent dosing of IV ketamine improves symptoms
An RCT (N = 67) evaluating twice- or thrice-weekly IV ketamine vs placebo in patients with recurrent depression (with at least 1 treatment failure) found that ketamine significantly improved standardized depression scores and response rates at 15 days. Patients with clinically significant suicidality were excluded.3
Researchers randomized patients to IV ketamine (0.05 mg/kg) twice or thrice weekly or to saline control and used the 60-point Montgomery-Asberg Depression Rating Scale (MADRS). A response was defined as a reduction of the MADRS score by 50%.
Both ketamine arms produced greater symptom improvement at 15 days, compared to placebo (twice weekly: −18.4 vs −5.7; P < 0.001; thrice weekly: −17.7 vs −3.1; P < 0.001) in addition to higher response rates (twice weekly: 69% vs 15%; P = .005; number needed to treat [NNT] = 2; and thrice-weekly: 54% vs 6%; P = .004; NNT = 2).3 There was no significant difference between twice- or thrice-weekly dosing. The study was flawed by dropouts (N = 57 at 15 days and N = 25 at 28 days), primarily attributed to ketamine adverse effects, that prevented assessment beyond 2 weeks.
Oral ketamine has a moderate effecton depression
A systematic review included 2 low-quality RCTs evaluating oral ketamine vs placebo as adjunctive treatment with sertraline, and oral ketamine vs diclofenac, and found improvement in patients with moderate depression.4 In the first RCT (n = 45), researchers found that oral ketamine (25 mg bid) plus sertraline (25 mg titrated up to 150 mg/d) produced more treatment responses (> 50% reduction on a standardized depression rating scale) than placebo plus sertraline (2 weeks: 85.4% vs 42.5%; P < .001; 6 weeks: 85.4% vs 57.5%; P = .005).4