• Cormac F Mullins, Sarah Walsh, Andrea Rooney, Connail McCrory, and Basabjt Das.
• Department of Anaesthesiology and Pain Medicine, St. James's Hospital, Dublin, Ireland. cormacmullins1@gmail.com.
• Ir J Med Sci. 2022 Apr 1; 191 (2): 859-864.

IntroductionChronic post-surgical neuropathic pain is difficult to treat. Topically applied analgesics provide an alternative to systemic therapy in localised neuropathic pain syndromes. The aim of this study was to prospectively assess whether 8% capsaicin is effective in surgically induced neuropathic pain.MethodologyPatients were screened for neuropathic pain using DN4 questionnaire. Validated questionnaires were completed at baseline and at 6 and 12 weeks (BPI, HADS, PGIC), and the affected area was mapped. The study received ethical approval from the local research ethics committee.ResultsThere were 12 participants. The most common operation was open thoracotomy (n = 8). There was a significant improvement in pain-interference from baseline to 12 weeks (p = .018). There were no significant changes in pain intensity or in the HADS. Repeat patches were performed for 4 participants on a second occasion (33%) and for 3 participants a third time (25%). There was a significant reduction in the surface area of the painful region on second (p = .04) and third applications (p = .023). At 12 weeks, 17% rated their symptoms very much better, 8% were much better, and 33% were minimally better, while 42% rated their symptoms no better.ConclusionsThis prospective study provides preliminary evidence for an improvement in patient outcomes with 8% capsaicin in surgically induced neuropathic pain. Improvements were noted in pain interference, and significant reductions in the painful surface area were noted for those who underwent subsequent treatments. Findings should be replicated in a randomised control trial to establish causation.© 2021. Royal Academy of Medicine in Ireland.

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