Real-world outcomes of intranasal esketamine and intravenous ketamine induction therapy for treatment-resistant depression in a community clinic: a retrospective cohort study

In a community psychiatric clinic, adults with treatment-resistant depression who received either intranasal esketamine or intravenous ketamine showed large reductions in depression severity, as measured by the PHQ-9 questionnaire. Both groups had similar average decreases of about 10 points, with response rates around 65–69% and remission rates of 23–32%. Most patients completed the induction phase, and no serious adverse events occurred. The study was not large enough to detect meaningful differences between the two treatments, and the different dosing schedules further limit direct comparison. The findings suggest both treatments are effective in real-world settings, consistent with prior controlled trials.

Study at a glance

Abstract

Introduction Intravenous (IV) ketamine and intranasal esketamine are NMDA receptor antagonists used for treatment-resistant depression (TRD). Both have demonstrated efficacy in controlled trials, but observational evidence from real-world community settings is limited. Methods We conducted a single-center retrospective cohort study of adults aged 18 to 65 receiving induction therapy for TRD with intranasal esketamine or IV ketamine at a community psychiatric clinic from January 1 through December 31, 2025. Patients with prior exposure to either medication or to oral ketamine derivatives were excluded. The primary outcome was change in Patient Health Questionnaire-9 (PHQ-9) score from baseline to end of induction. Secondary outcomes included response (≥50% PHQ-9 reduction), remission (final PHQ-9 ≤4), clinically meaningful improvement (≥5 PHQ-9 reduction), induction completion, and adverse events. Within-group and per-protocol analyses were exploratory. Results Sixty-three patients met inclusion criteria (esketamine n=37; IV ketamine n=26). Baseline PHQ-9 scores were similar (18.22±4.49 vs. 18.27±5.41; P = 0.967), as was mean change from baseline (-10.31±5.59 vs. -9.50±5.69; mean difference 0.81, 95% CI -2.12 to 3.75; P = 0.589). Response rates were 64.9% vs. 69.2% (RR 0.94, 95% CI 0.66 to 1.33; P = 0.790), remission 32.4% vs. 23.1% (RR 1.41, 95% CI 0.61 to 3.26; P = 0.573), and clinically meaningful improvement 83.8% vs 73.1% (RR 1.15, 95% CI 0.87 to 1.51; P = 0.353). Induction completion exceeded 90% in both groups; one patient per cohort discontinued from intolerable side effects, and no serious adverse events occurred. Within-group PHQ-9 reduction was large: 10.31±5.59 points (paired t[34]=10.91; P<0.001; Cohen’s d=1.84) for esketamine and 9.50±5.69 points (paired t[23]=8.18; P<0.001; Cohen’s d=1.67) for ketamine. Findings remained statistically significant and clinically large under a pre-specified baseline observation carried forward (BOCF) sensitivity analysis (Cohen’s d=1.65 and 1.45). Conclusions Induction therapy with intranasal esketamine and intravenous ketamine was associated with robust antidepressant effects in a community outpatient setting, consistent with prior trial data. The modest sample size limits power to detect between-group differences and increases the risk of type II error; the absence of statistically significant between-group differences should therefore not be interpreted as evidence of equivalence. Protocol asymmetry between arms (esketamine: 12 sessions over 8 weeks; IV ketamine: 6 sessions over 3 weeks) further limits direct comparison of endpoint values between groups. Practical considerations including insurance coverage, cost, and administration logistics may help guide treatment selection. Longitudinal follow-up is planned to characterize treatment durability.