Efficacy and safety of oral ketamine versus diclofenac to alleviate mild to moderate depression in chronic pain patients: A double-blind, randomized, controlled trial.

Background: Ketamine is a glutamate N-methyl-d-aspartate receptor antagonist capable of exerting antidepressive effects in single or repeated intravenous infusions. The objective of this study was to investigate the safety and the efficacy of oral ketamine vs. diclofenac monotherapy in reducing symptoms of mild to moderate depression among patients with chronic pain.

Methods: This study is a 6-week, randomized, double-blind, controlled, parallel-group trial with two intervention arms (ketamine, fixed daily dosage of 150mg vs. diclofenac, fixed daily dosage of 150mg). Twenty participants in each arm completed the trial program all of whom had two post-baseline measurements at week 3 and week 6. Reduction in depression symptoms was assessed using the Hamilton Depression Rating Scale (HDRS) and the hospital anxiety and depression subscale for depression (HADSDepression) scores at baseline and week 3 and week 6 post-intervention.

Results: Significantly lower HDRS scores were observed in the ketamine treatment group as early as 6 weeks post-intervention (P=0.008). By comparison, mean (±standard deviation) HADS depression subscale scores were significantly lower for individuals receiving ketamine compared to diclofenac for both post-baseline measures at week 3 (6.95±1.47 vs. 8.40±1.6, P=0.005) and week 6 (6.20±1.15 vs. 7.35±1.18, p=0.003).

Limitations: The limitations of the present study were its small sample size and the short-term follow-up period.

Conclusions: Oral ketamine appears to be a safe and effective option in improving depressive symptoms of patients with chronic pain with mild-to-moderate depression.