1. 2020;23;E541-E5488% Capsaicin Patch in Treatment of Peripheral Neuropathic Pain
   Observational Report
   Paula Barbosa, MD, Virginia Rebelo, MD, Decia Goncalves, MD, and Armanda Gomes, MD.

BACKGROUND: Neuropathic pain is a complex condition that is difficult to control and has a high impact on quality of life. 8% Capsaicin patch can be a therapeutic strategy in the treatment of peripheral neuropathic pain.

OBJECTIVES: This study aims to (1) evaluate clinical efficacy and (2) tolerability of 8% capsaicin patch in a Pain Unit.

STUDY DESIGN: Retrospective observational study

SETTING: Portuguese Pain Unit

METHODS: A sample of 120 patients diagnosed with peripheral neuropathic pain, underwent treatment with the 8% capsaicin patch between February 2011 and February 2019 in a Portuguese Pain Unit. Patients were included in one of the following groups according to the etiology of pain: postherpetic neuralgia (PHN), chronic post-surgical pain (CPSP), post traumatic neuropathic pain (PTNP), diabetic neuropathy (DN), regional pain syndrome. complex I and II (CRPS I / II), HIV-associated neuropathy (HIVN), lumbar neuropathic pain (LNP), trigeminal neuralgia (TN) and other neuropathies (O).  The evaluated parameters were: pain intensity according to unit protocol (numerical rating scale), pain characteristics, location, size of the painful area. The evolution of pain intensity after treatment (patients were considered as responders to therapy if the decrease in NRS was equal to or greater than 30%; patients with a decrease in NRS of 50% or more were also analyzed), the area of pain and the need for adjuvant analgesic therapy, as well as the tolerability to treatment and the identification of eventual predictors of its efficacy were evaluated, at 15 days, 8 weeks and 12 weeks after 8% capsaicin patch.

RESULTS: Of the 120 patients in the sample, 40.8% had a >= 30% decrease in basal pain intensity 15 days after treatment, 43.3% after 8 weeks and 45.0% after 12 weeks. 30.8% of patients had >= 50% decreased basal pain intensity 15 days after treatment, 27.5% after 8 weeks and 30.0% after 12 weeks. Pain area decreased in 36.7% of patients and 18.3% reduced chronic analgesic therapy within 12 weeks after 8% capsaicin patch application. There was only one case of intolerance to the treatment.

LIMITATIONS: This study has the limitations inherent to a retrospective study. The study period was only 12 weeks and some diagnostic groups included a small number of patients.

CONCLUSION: Treatment of peripheral neuropathic pain with 8% capsaicin patch seem to be effective in the short and medium term, both in decreasing pain intensity and in reducing the painful area. Its application is tolerated by most patients.

KEY WORDS: 8% capsaicin patch, peripheral neuropathic pain, pain intensity, painful area