Ketamine for refractory chronic pain: a 1-year follow-up study

Area of Science:

• Anesthesiology and Pain Management
• Pharmacology
• Clinical Research

Background:

• Long-term efficacy of ketamine for refractory chronic pain is not well-documented.
• Ketamine is increasingly used in pain clinics for difficult-to-treat chronic pain conditions.

Purpose of the Study:

• To evaluate the long-term (1-year) effects of ketamine on pain intensity and health variables in patients with refractory chronic pain.
• To identify distinct pain trajectories and factors influencing ketamine's effectiveness.

Main Methods:

• A prospective, multicenter, 1-year observational study involving 256 patients across 30 French pain clinics.
• Monthly assessment of pain intensity using a numerical rating scale.
• Semiparametric mixture models were used to identify pain trajectories and analyze adverse events.

Main Results:

• Significant decrease in pain intensity from baseline (6.8) to 12 months (5.7) (P < 0.001), with a moderate effect size (0.61).
• Three distinct pain trajectories were identified: mild (16.0%), moderate (35.3%), and severe (45.7%), with neuropathic pain and fibromyalgia showing different outcomes.
• Adverse events were reported by 50% of patients at 1 week, decreasing over time. Pain severity correlated with anxiety, depression, and reduced quality of life.

Conclusions:

• Ketamine treatment demonstrated a significant long-term reduction in pain intensity for refractory chronic pain patients.
• Distinct patient subgroups (pain trajectories) respond differently to ketamine, suggesting a need for personalized treatment approaches.
• Optimizing patient subtyping is crucial for enhancing the safety and efficacy of ketamine therapy in chronic pain management.