Pain Physician. 2005;8:175-179, ISSN 1533-3159
Michael E. Goldberg, MD, Richard Domsky, MD, Denise Scaringe, MD, Robert Hirsh, MD, Jessie Dotson, MSN, Imran Sharaf, MD, Marc C. Torjman, PhD, and Robert J. Schwartzman, MD
Department of Anesthesiology, Division of Pain Management, Cooper University Hospital, The Robert Wood Johnson Medical School, Camden, NJ; and Department of Neurology, Drexel University College of Medicine, Philadelphia, PA
Complex Regional Pain Syndrome Type 1 (CRPS-1) responds poorly to standard pain treatment. We evaluated if the N-methyl-D-aspartate receptor antagonist S(+)-ketamine improves pain in CRPS-1 patients. Sixty CRPS-1 patients (48 females) with severe pain participated in a double-blind randomized placebo-controlled parallel-group trial. Patients were given a 4.2-day intravenous infusion of low-dose ketamine (n = 30) or placebo (n = 30) using an individualized stepwise tailoring of dosage based on effect (pain relief) and side effects (nausea/vomiting/psychomimetic effects). The primary outcome of the study was the pain score (numerical rating score: 0–10) during the 12-week study period. The median (range) disease duration of the patients was 7.4 (0.1–31.9) years. At the end of infusion, the ketamine dose was 22.2 ± 2.0 mg/h/70 kg. Pain scores over the 12-week study period in patients receiving ketamine were significantly lower than those in patients receiving placebo (P < 0.001). The lowest pain score was at the end of week 1: ketamine 2.68 ± 0.51, placebo 5.45 ± 0.48. In week 12, significance in pain relief between groups was lost (P = 0.07). Treatment did not cause functional improvement. Patients receiving ketamine more often experienced mild to moderate psychomimetic side effects during drug infusion (76% versus 18%, P < 0.001). In conclusion, in a population of mostly chronic CRPS-1 patients with severe pain at baseline, a multiple day ketamine infusion resulted in significant pain relief without functional improvement. Treatment with ketamine was safe with psychomimetic side effects that were acceptable to most patients.