Background The name of carpal tunnel syndrome (CTS) refers to a complex of symptoms resulting from the pressure exerted on the median nerve in the carpal tunnel area. CTS is the most frequent pressure neuropathy. The treatment of chronic neuropathic pain or mixed states of chronic neuropathic-inflammatory pain is difficult. The conservative treatments that currently exist are only moderately effectively. Oral pharmaceuticals for neuropathic pain have significant side effects, and treatment efficacy tends to be modest. The use of topical analgesics reduces the potential for systemic side effects and allows direct application of medications to the area of pain. Capsaicin, once applied to the skin, causes a brief initial sensitization followed by a prolonged desensitization of the local pain nerves. This occurs through stimulation of the transient receptor potential vanilloid-1 (TRPV1) expressing pain nerve fibers. Capsaicin dermal is an adhesive patch containing a high concentration (8%) of synthetic capsaicin. It is indicated for the treatment of peripheral neuropathic pain in non-diabetic patients. But it has not been studied yet in patients with CTS.
Objectives The aim of this study was to evaluate the efficacy of 8% capsaicin dermal patch in the treatment of neuropathic pain resulting from CTS.
Methods The patients with clinically and electrophysiologically confirmed CTS, indicated for the treatment of highly concentrated capsaicin 8% patch due to neuropathic pain, were included in the study. The aim of the study was to determine the proportion of patients who achieve at least a 30% reduction in pain intensity on the Numeric Pain Rating Scale (NPRS) compared with baseline. Patients were monitored in two visits - before treatment of capsaicin patch and after 3 months of application. On both visits were evaluated clinical status, monitored the intensity of pain and quality of life. The intensity of pain was evaluated using a range of intensity of pain – NPRS. This is a point scale with a range of values 0-10, the patients express the average pain intensity in the last 24 hours. Quality of life was assessed using the EQ-5D questionnaire.
Results Altogether, 28 patients (four male) with symptomatic CTS were included in this study between April 2012 and October 2013. Out of these patients 15 had CTS due to rheumatoid arthritis, 3 due to crystal induced rheumatoid diseases, 2 due to psoriatic arthritis and 8 due to other diseases. Capsaicin dermal patch reduced NPRS scores from baseline 6.3 points to 3.4 points after 3 months treatment (p<0.001). 71% of patients experienced at least a 30% reduction of pain intensity measured with NPRS score, 64% of patients had at least a 50% reduction of pain intensity. The quality of life assessed by EQ-5D questionnaire improved significantly from 0.51 to 0.69 (three months after patch administration, p<0.001). The consumption of concomitant medication decreased from 81% of patients at baseline to 52% after 3 months. Capsaicin dermal patch was well tolerated. The most common adverse events were transient, mostly mild, application reaction in 8% of patients.
Conclusions Capsaicin in the form of 8% dermal patch is a new treatment option for peripheral neuropathic pain in patients with carpal tunnel syndrome. This study showed a high therapeutic efficacy, excellent tolerability and a significant improvement in quality of life, persisting for at least 3 months after administration.
Acknowledgements This work was supported by the project (Ministry of Health, Czech Republic) for consensual development of research organization 023728.
Disclosure of Interest : None declared