Topical Ketamine in the Treatment of Complex Regional Pain Syndrome

The purpose of this study was to evaluate the effectiveness and adverse effects of topical ketamine in the treatment of complex regional pain syndrome. Retrospective charts were reviewed of patients 18 years or older diagnosed with complex regional pain syndrome and treated with topical ketamine during the study period of May 2006 to April 2013 in an academic medical center specialty pain clinic. Exclusion criteria consisted of subjects who 1) were treated with topical ketamine for pain syndromes other than complex regional pain syndrome, 2) initiated other pain therapies concurrently with topical ketamine, 3) had less than two documented visits, 4) began use of topical ketamine prior to the start of the study period, 5) were under 18 years of age. Subjects with ICD-9 diagnoses codes complex regional pain syndrome-1 or complex regional pain syndrome-2 were identified from encounter-based data and billing records. Data collected for each subject included demographics, description of complex regional pain syndrome, concurrent medications and medical conditions, type of ketamine compound prescribed, duration of therapy, side effects, reasons for discontinuation (if any), and pain scores (numerical pain rating scale; 0 to 10). Data were analyzed using descriptive statistics. Institutional Review Board approval was obtained prior to initiating the study. Sixteen subjects met the inclusion/exclusion criteria for the study, 69% of which were female with an average age of 46 years (range: 24 to 60). Subjects took an average of 3.7 other pain medications (range: 2 to 8), had an average of 2.7 other co-morbid pain conditions (range: 1 to 5), and 1.6 other co-morbid non-pain conditions (range: 0 to 4). Eight (50%) reported that their pain had improved, while 7 (44%) reported a worsening of pain. One reported no change in pain score. No subjects reported adverse effects. Based on the findings in this study, the use of topical ketamine in the treatment of complex regional pain syndrome shows promise due to the overall limited options available to treat this condition, as well as the favorable safety profile of topical agents. Future prospective controlled studies are needed to demonstrate a clear benefit.