Six weeks open-label oral ketamine for patients with treatment-resistant depression, post-traumatic stress disorder, or obsessive-compulsive disorder.

Background: We previously completed a double-blind randomised crossover study assessing intramuscular ketamine for treatment-resistant depression (TR-D), post-traumatic stress disorder (TR-PTSD) and obsessive-compulsive disorder (TR-OCD). Here, we report an extension study to explore the ongoing benefits and tolerability of maintenance oral ketamine.

Method: All participants from the original study were eligible to receive a 6-week open-label course of oral ketamine once-thrice weekly. Racemic ketamine for injection was diluted in orange juice and sipped over 30-60 min. Dose amount and frequency were adjusted individually to maximise benefits and tolerability. Effectiveness was assessed by disorder-specific scales. Side effects and tolerability were assessed using reported adverse events and scales for dissociation and urinary/bladder symptoms.

Results: Seventeen participants with TR-D, 18 participants with TR-PTSD and 8 participants with TR-OCD commenced oral ketamine. Nine participants with TR-D, 16 participants with TR-PTSD and 5 participants with TR-OCD completed all 6 weeks of dosing. Ketamine dose increased over time from 1-1.5 mg/kg to 1.5-2.5 mg/kg, with a dosing frequency of 1-3 times/week, with an average total dose rising from 1.9 to 3.0 mg/kg/week over the first 3 weeks. Symptom rating scores for TR-D, TR-PTSD and TR-OCD were low at week 1 of oral dosing (compared to scores at entry into the original study) and remained low throughout the six-week course of oral ketamine. Oral ketamine was well tolerated with minimal side effects.

Conclusion: The 6-week extension of oral ketamine appeared to sustain improvements for TR-D, TR-PTSD and TR-OCD. Oral ketamine was well tolerated and offers an alternative option for patients, researchers and clinicians.