Objective: This open-label clinical trial examined the preliminary efficacy of combining a course of 6 ketamine infusions with a brief, evidence-based exposure-based psychotherapy—written exposure therapy (WET)—in patients with chronic posttraumatic stress disorder (PTSD).

Methods: The trial was conducted between June 2021 and October 2023. Patients with chronic PTSD and high-moderate to severe symptom levels received 6 intravenous ketamine infusions (0.5 mg/kg), 3 times a week for 2 consecutive weeks, plus 5 WET sessions over 2 weeks, beginning after the first 4 infusions and administered on different days than infusion days. The primary outcome was change in the Clinician Administered PTSD Scale for DSM-5 (CAPS-5) scores from baseline (before the first infusion) to 12 weeks from start of WET (“Week 12”).

Results: Fourteen eligible patients began treatment, and 13 completed all infusions and WET. The combined treatment was associated with large-magnitude improvement in PTSD symptom severity from baseline (mean CAPS 5 = 41.6 [SD = 6.2]) to Week 12 (CAPS 5 = 20.8 [14.8], Cohen d [95% CI] = 1.9 [1.0–2.8], P < .001). Nine (69%) patients were treatment responders (≥30% improvement on the CAPS-5). Response was rapid and also durable in 8 (61.5%) patients, assessed up to 6 months from baseline.

Conclusions: Preliminary findings from this open-label clinical trial suggest that the combined treatment may yield large magnitude and durable reductions in PTSD symptoms for patients with more severe chronic PTSD. Large-scale randomized controlled trials are needed to determine the efficacy and potential synergistic effect of this promising combined treatment in this patient population.

Trial Registration: ClinicalTrials.gov identifier: NCT04889664

J Clin Psychiatry 2025;86(2):24m15622

Author affiliations are listed at the end of this article.

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